Your Project Architecture — Clean End-to-End Flow
1. Frontend (Angular + Web Components)
- You have a main Angular app (
www.wecode.com) → It contains multiple sub-apps as Web Components (micro frontends) - Routing inside Angular decides which Web Component (sub-app) to load
- Each Web Component calls its own backend API (via domain like
api.wecode.com/students-api/...)
2. API Gateway (Apigee)
- All frontend API calls go to Apigee first (not directly to services)
-
Apigee responsibilities:
- Authentication & Authorization (with Okta)
- Rate limiting, caching, security policies
- Routing requests to appropriate backend microservices
(e.g., route
/students-api/...→ to Students Service)
3. Backend Services (Spring Boot Microservices)
- Each API (like
/students-api) is backed by a Spring Boot service - Developers code the microservice → builds with Jenkins
- Jenkins builds Docker images and pushes them to Private Docker Registry (
artifactory.wecode.com)
4. Deployment (GitOps + Spinnaker + Kubernetes)
- You have GitOps repos (YAML manifests) → One per service + env (dev, qa, prod)
-
You update:
- Docker image tag (new build)
- Replica count (number of Pods)
- Spinnaker watches GitOps repo → Automatically triggers deployment to Azure Kubernetes cluster
- K8s creates/updates Pods for each microservice → You verify running Pods via Azure cloud dashboard
5. Auth Flow (Okta)
- Frontend gets JWT tokens (OAuth / OIDC) from Okta
- Frontend sends token in Authorization header of every API call
- Apigee validates token (with Okta) before routing to backend
- If token invalid/expired → Apigee returns 403 error
6. High Availability + Scalability
- Apigee handles external load balancing + API security
-
Kubernetes handles:
- Service discovery
- Internal load balancing (across Pods)
- Auto-healing (restarts Pods if they fail)
- Scaling (manual/auto based on load)
Clean Diagram (Mental Model)
User Browser
↓
www.wecode.com (Angular + WebComponents)
↓
api.wecode.com (Apigee API Gateway)
↓
Apigee Auth (Okta) + Routing
↓
Azure Kubernetes Cluster
┌─────────────────────────────┐
│ Students Service (Pods) │
│ Courses Service (Pods) │
│ Payments Service (Pods) │
└─────────────────────────────┘
↓
Databases / Other services
What to say in interview? (Clean summary)
“We have a micro-frontend architecture where an Angular app loads various Web Components, each calling its respective backend APIs via Apigee API Gateway. Apigee handles authentication (via Okta), security, and routing. Backend microservices are Spring Boot apps containerized via Jenkins and stored in a private Docker registry. Deployments are fully automated using a GitOps model where Spinnaker triggers Kubernetes deployments (Azure AKS) based on YAML manifest updates. Kubernetes ensures service discovery, load balancing, scaling, and self-healing.”
Why is this modern and scalable? (If interviewer asks)
- API Gateway decouples security/routing from services
- Micro-frontends enable independent feature delivery
- CI/CD (Jenkins + Spinnaker + GitOps) gives safe, automated deploys
- Kubernetes handles infra resilience and scalability
Why you get errors like “Only X characters allowed” / “Max 10 MB data allowed”
These types of errors are API Gateway policy enforcement errors — not directly from your backend service.
Apigee sits in front of all your backend APIs and it applies policies like:
| Policy Type | Example |
|---|---|
| Request/Response Size Limits | Max request payload size = 10MB |
| Header Size Limit | Max header length = X characters |
| Query Param Validation | Max param length, allowed patterns |
| Content Type Validation | Only accept JSON, not XML |
| Rate Limits / Quotas | Max 1000 requests per minute |
| Timeouts | Request must finish in X seconds |
| Security Policies | Disallow file uploads over X MB |
If any of these policies fail, Apigee throws an error before even calling your backend service That’s why:
- You see 400/413 errors
- Or messages like “Payload too large”, “Parameter too long”
Real Example (Apigee policy config)
Here’s how an Apigee policy to limit payload might look:
<Step>
<Name>VerifyPayloadSize</Name>
</Step>
<Javascript name="VerifyPayloadSize">
<Properties>
<Property name="maxPayloadSize">10485760</Property> <!-- 10 MB -->
</Properties>
<ResourceURL>jsc://verifyPayloadSize.js</ResourceURL>
</Javascript>
Or directly with a built-in policy:
<SpikeArrest name="limit-payload">
<Properties>
<Property name="maxRequestSize">10MB</Property>
</Properties>
</SpikeArrest>
Clean interview explanation (if asked)
“Apigee can enforce API governance policies like payload size limits, header size limits, query param validation, and content type restrictions. When we see errors like ‘only 10 MB allowed’ or ‘param too long’, those are typically enforced by Apigee policies to protect backend services and ensure API stability.”
Bonus — Why these limits exist (good to mention in interview)
- Prevent DoS attacks (user sends 1GB file → server crashes)
- Ensure fair usage and predictable performance
- Protect backend services from unexpected large data
- Enforce API contract consistency (like max 255 chars param)
How to confirm it’s Apigee error (in real project)
- Check Apigee response code — usually it returns 4xx with policy error message
- Backend service logs — If backend was not hit at all → it’s Apigee
- Apigee policies config — Your Apigee team can confirm configured limits
Short answer: Yes, those limits are coming from Apigee, not from your backend Spring Boot service.
What is Axway? (In your project context)
In your project, Axway is used as an API Management / API Security Gateway, very similar to Apigee. It helps with:
- Managing API specifications / API contracts (like OpenAPI specs)
- Governing which APIs are officially exposed and allowed
- Controlling access control, API lifecycle, and API publishing
Basically:
Axway is maintaining the “official allowed API catalog”. If an API is not registered/declared properly in Axway → it is considered unauthorized → you get 403 Forbidden.
Your GitOps repo → Axway folder → API Specs
That folder contains:
- API specifications (OpenAPI / Swagger files)
- Policies or metadata saying which APIs are published, versioned, allowed
When you deploy a new backend service (say “Students API”) — If that API’s spec is not present or not registered correctly in the Axway repo, Axway blocks requests to it and returns 403 Forbidden (“This API is not allowed / not published / not authorized”)
Clean flow of what’s happening
Frontend Angular
↓
api.wecode.com (Apigee API Gateway)
↓
→ Apigee authenticates token (Okta)
→ Apigee checks routing
Apigee sends request to:
↓
Axway API Manager
→ Is this API spec registered and allowed? (From GitOps Axway folder)
- Yes → forward to backend service
- No → 403 Forbidden (blocked)
↓
Backend Spring Boot Service (in Kubernetes)
Why are both Apigee AND Axway used?
In many enterprises (like yours), Apigee is used mainly as the external API Gateway (handling client traffic, security, token validation)
And Axway is used as a central API management / governance platform to:
- Manage API specs, versioning, catalog
- Control which APIs are published / allowed
- Govern internal APIs and partner APIs (Sometimes it enforces more strict enterprise-level policies)
Interview-ready explanation (if asked)
“In our project, Apigee handles external API Gateway tasks like authentication and routing, while Axway governs API specifications and ensures only registered, approved APIs are accessible. If a new backend API is deployed but not registered in Axway via our GitOps specs folder, Axway blocks the request and returns a 403 Forbidden error, ensuring API governance and security compliance.”
So to answer you clearly
Yes — the 403 Forbidden you mentioned (for new APIs) → It is because Axway is blocking that API due to missing or unregistered spec → You need to add the API spec in GitOps Axway folder to allow traffic
Axway is not specific to your project; it’s actually a well-known, enterprise-grade API management platform used by many organizations for managing, securing, and governing APIs.
So, Axway is a real product and is commonly used in industries that deal with complex API ecosystems, needing advanced control over their APIs, such as:
- API Gateway
- API Security
- API Lifecycle Management
- Analytics and Monitoring for APIs
- Developer Portals
Key Features of Axway:
- API Gateway: Manages API traffic and secures it (similar to Apigee). It supports rate limiting, authentication, API routing, and more.
- API Management: Allows enterprises to define, register, and control which APIs are exposed (and which are not). Provides security policies, access control, versioning of APIs.
- Security: Enforces security policies like OAuth, rate limiting, throttling, and more. It also helps with monitoring and logging.
- API Analytics: Offers analytics to track usage patterns, error rates, and API performance metrics.
- API Lifecycle: It helps manage the entire lifecycle of an API (from design to deprecation).
Axway in General
Axway is widely used across many industries, not just yours. Some of the use cases for Axway could include:
- Banking & Financial Services: Managing secure APIs to allow third-party services to interact with their systems.
- Retail: Managing the API traffic between web applications and internal systems.
- Healthcare: Securing API interactions between hospitals, pharmacies, and insurers.
Axway API Management Solutions Include:
- Axway API Gateway: A powerful tool to secure, scale, and monitor APIs.
- Axway Amplify: A platform that helps businesses with API integration and delivery.
- Axway Centralized Analytics: For monitoring and analyzing API traffic.
Axway’s Role in Your Project
In your specific project, it seems that Axway is playing the role of API Governance. You are using it for managing and securing your APIs (defining which are allowed, handling access control, etc.). When you get errors like 403 Forbidden for new APIs, it’s because Axway hasn’t registered or authorized that API yet.
Short Explanation for Interview/Clarity:
“Axway is an API management and governance platform used for securing and managing APIs. It allows enterprises to define, monitor, and control which APIs are exposed to clients. In our case, Axway is used to ensure that only approved and registered APIs are accessible. When new APIs are deployed but not registered, Axway blocks them, leading to 403 errors.”
So, Axway is a product used for API management and is not something unique to your project. It’s widely used in the industry for complex API ecosystems.
Your Frontend Setup: Micro Frontends Using Web Components
You have:
- One Main Angular app (like
wecode-frontend) - Several sub-applications (small Angular apps or other apps), built as Web Components
Each sub-app is:
- In a separate Git repo
- Built independently (just like backend services)
- Deployed separately (maybe to some cloud storage, CDN, or server)
These sub-apps are Web Components — meaning:
- They are compiled into custom HTML elements (like
<student-app></student-app>,<teacher-app></teacher-app>, etc.) - They are framework-agnostic (once built, you can use them in any app, not just Angular)
How Main Frontend Loads These Web Components
1. Build and Host
Each micro frontend (web component) is built separately → produces JavaScript bundles (e.g., student-app.js).
These JS bundles are uploaded somewhere (S3 bucket, Azure blob storage, or static servers).
2. Main App Loads Dynamically
In the main Angular app:
-
You have a configuration (like in package.json, or a config file) where you define:
- URL to load the web component (JS file)
- Name of the custom element (e.g.,
<student-app>)
-
When user navigates to a certain route (say
/students), → The main app dynamically loads that JS bundle at runtime → Browser registers the new web component → You render the custom element like a normal HTML tag
Example:
<!-- Inside Main Angular App -->
<student-app></student-app>
Behind the scenes:
- Main app downloads
student-app.js - Registers it
- Shows the Student Application seamlessly inside the main app
Summary of the Full Flow
| Step | What happens |
|---|---|
| 1 | Each web component is built separately and hosted somewhere |
| 2 | Main Angular app has a config mapping URL and web component name |
| 3 | When user navigates to a specific route, the main app loads the JS bundle |
| 4 | Browser registers the Web Component |
| 5 | Main app renders the custom element like a normal Angular component |
| 6 | Web component runs its own Angular code internally, independent of main app |
Bonus: Why this Micro Frontend Architecture?
- Teams can develop/deploy independently
- Faster builds (small apps instead of a huge monolith)
- Different tech stacks possible (though all yours are Angular for now)
- Easy scaling and modularization
Small Interview-Ready Summary
“In our project, we use a micro frontend architecture where each web component is a separately developed and deployed application. The main Angular app dynamically loads these web components based on user navigation. It treats them like standard HTML elements, allowing independent deployment and scaling of different parts of the application.”
1. What is Docker?
Docker is a tool that packages your application (code + dependencies + environment) into a Docker Image. That image can run anywhere (on your laptop, server, cloud) — exactly the same way.
Why do we use Docker?
Because:
- No more “It works on my machine” problem
- The same Docker image can run in dev, QA, stage, prod — no surprises
- Easy to deploy, scale, and manage applications
Example
Your Student Service (Spring Boot app) → You want to Dockerize it.
You write a Dockerfile:
FROM openjdk:17-jdk
COPY target/student-service.jar app.jar
ENTRYPOINT ["java", "-jar", "/app.jar"]
When you run docker build, it creates a Docker Image → e.g.,
student-service:v1.0
This image contains:
- JDK
- Your compiled
.jarfile - Everything needed to run it
2. What is Artifactory?
Artifactory is like a storage or repository (just like Git stores code, Artifactory stores built artifacts). In your case, it stores Docker images and maybe JARs, NPM packages, etc.
You can think of it as:
“A private DockerHub / Maven Central for your company.”
Why do we use Artifactory?
Because:
- Company wants to store all Docker images privately
- You can version your images →
student-service:v1.0,v2.0, etc. - Secure access, faster downloads within organization
Example Flow
| Step | What happens |
|---|---|
| 1 | You build Docker Image of Student Service on Jenkins |
| 2 | Jenkins pushes that image to Artifactory (your private Docker registry) |
| 3 | During deployment, Kubernetes pulls that image from Artifactory and deploys it |
Your Project Flow — Docker + Artifactory
- Developer writes code (Spring Boot)
- Jenkins builds the code → creates Docker image
→ e.g.,
student-service:v1.2 - Jenkins pushes that image to Artifactory →
artifactory.wecode.com - You update
.yamlfile (GitOps repo) with new image tag → e.g.,image: artifactory.wecode.com/student-service:v1.2 - Spinnaker sees the change and triggers deployment on Kubernetes
- Kubernetes pulls image from Artifactory → runs it in a pod
Quick 1-Line Definitions (For Interview)
| Tool | Simple Definition |
|---|---|
| Docker | Packages application + dependencies into portable container images |
| Artifactory | Private repository to store Docker images (and other artifacts) securely |
| Jenkins | CI/CD tool to automate build, test, and deployment |
| Spinnaker | Continuous delivery tool to automate deployments (works with K8s) |
Your Interview-Ready Summary
“In our project, we use Docker to package backend services into images. Jenkins builds and pushes these images to our private Artifactory (Docker registry). Kubernetes then pulls the images from Artifactory and deploys them in pods, ensuring consistent environments across all stages.”
[End Users (Browser)]
↓
[Frontend (Angular)]
↓ REST API calls
[Apigee Gateway (API Proxy)]
↓ Routes to
[Kubernetes Cluster]
↓
[Spring Boot Backend (Deployed as Pod)]
↓
[PostgreSQL DB (K8s Service)]
1️⃣ What is Microservices Architecture? (Clear and Crisp)
Microservices Architecture is an approach where an application is built as a collection of small, independent services, each responsible for a specific business capability, and they communicate with each other over lightweight protocols (like REST APIs, messaging queues).
🔹 Core Characteristics
| Principle | Meaning |
|---|---|
| Independent deployability | Each service is deployed separately |
| Single Responsibility | Each service does one business function |
| Decentralized Data | Each service owns its data, though in real world shared DBs exist too |
| Technology Diversity | Services can use different languages / databases |
| Resilience | Failure of one service doesn’t bring down the entire system |
| Elastic Scaling | Services scale independently |
| DevOps Automation | CI/CD pipelines, containerization, orchestration (e.g., K8s) |
2️⃣ Your project — Full Microservices Architecture (Explained Clearly)
Here’s how YOUR project fits cleanly into a modern microservices architecture:
🖥️ Frontend (Client Layer)
-
Single Page Angular App (SPA) → A modern frontend, loading dynamic web components on demand
-
Web Components (micro-frontends pattern) → Each sub-module downloads
main.jsof that component dynamically → Managed via Artifactory NPM registry -
Authentication (Frontend) → Separate Auth Repository (shared) used as npm dependency → Integrates with Okta → On app load → Redirect to Okta → Get token → Pass token as Bearer in all API calls
🌐 API Gateway Layer
-
Apigee (API Gateway) → Validates the bearer token from frontend (token verification) → Routes API requests to correct microservice backend based on path → Provides centralized:
- Rate limiting
- Authentication enforcement
- Routing
-
Axway → Acts as a policy enforcement and validation layer → Rejects API calls if APIs not configured correctly
⚙️ Backend (Microservices Layer)
-
Multiple Spring Boot Services exposed like: →
apidev.xyz.com/payments→apidev.xyz.com/accounts→ … etc. -
Service-to-Service Communication → Via Kafka (event-driven) and REST APIs
-
Authentication (Backend) → Separate Spring Security Auth Repository → Shared as Maven dependency in backend microservices → Uses annotations like
@RolesAllowed→ Fine-grained API access control → Validates roles and permissions automatically
🛢️ Database Layer (Persistence)
-
Polyglot Persistence (Multiple DBs) → Oracle DB (for transactional services) → MongoDB (for document-oriented services)
-
Data Ownership → Some services have separate DB (ideal microservices pattern) → Some share a common DB (practical compromise — real-world pattern)
📦 Infrastructure & DevOps Layer
-
Kubernetes (Azure Red Hat OpenShift) → Used to deploy and manage all microservices → Scaling via replicaCount → Logs monitored via Azure OpenShift and ElasticSearch (historical logs)
-
GitOps (CI/CD) → GitOps repo stores Kubernetes manifests → Only changes like
replicaCountanddocker image tag→ On code push:- CI builds Docker image
- Pushes to Docker Artifactory
- GitOps pulls new image tag and deploys via Kubernetes
-
Elastic Stack (ELK) → Centralized logging and monitoring → Searchable logs for debugging, historical audits
📊 Documentation & Developer Experience
- Swagger/OpenAPI Docs → All backend APIs are documented for developers
🗺️ Full Diagram (Textual View)
[Angular SPA] --> [Okta Auth] --> [Bearer Token]
│
▼
[Apigee API Gateway] --> [Axway (Policy Validator)]
│
┌──────────────┬─────────────┐
▼ ▼ ▼
Payments Svc Accounts Svc Other Svc
own DB shared DB own DB
Oracle/Mongo Oracle/Mongo Oracle/Mongo
│ │
Kafka / REST Kafka / REST
│ │
┌──────────────┴─────────────┐
▼ ▼
[Elastic Logs] [GitOps (K8s Deployments)]
│
Docker Images (Artifactory)
✅ Why YOUR project is clearly Microservices Architecture
| Microservices Characteristic | Your Project |
|---|---|
| Independent services | Payments, Accounts, etc |
| API Gateway | Apigee |
| Decentralized data | Separate + Shared DBs |
| Polyglot persistence | Oracle + MongoDB |
| Lightweight comm | REST + Kafka |
| Independent deployability | Via Docker + K8s |
| Authentication | Okta + Spring Security shared repo |
| DevOps automation | CI/CD + GitOps + Kubernetes |
| Observability | Elastic Logs |
| Documentation | Swagger / OpenAPI |
📝 How to explain in interview (summary answer)
“Yes, we follow a microservices-based architecture in our project. We have multiple Spring Boot-based services like Payments and Accounts, independently deployed and exposed behind Apigee API Gateway. Our frontend is an Angular SPA that integrates with Okta for authentication. Backend services communicate using REST APIs and Kafka for async processing. We use a combination of Oracle and MongoDB for persistence. Kubernetes on Azure OpenShift manages our deployments via GitOps pipelines. CI/CD builds Docker images and pushes to Artifactory. We have centralized logging using Elastic Stack and document all APIs using Swagger. We also enforce fine-grained API security using Spring Security with role-based access controls.”
📝 Advanced Microservices Interview Q\&A (Customised to Your Project)
Q1. What is microservices architecture and how is it applied in your project?
Answer: Microservices architecture breaks a large application into small, independently deployable services, each responsible for a specific business capability.
In our project, we have multiple Spring Boot-based microservices such as Payments, Accounts, etc., exposed as independent APIs (apidev.xyz.com/payments, etc.). These services are behind an Apigee API Gateway, and they communicate using REST APIs and Kafka (for asynchronous messaging). Each service is independently deployed via Kubernetes and CI/CD pipelines.
Q2. How do you manage authentication and authorization in your microservices?
Answer: Authentication is handled using Okta. Our Angular SPA redirects users to Okta for login, and once authenticated, we receive a Bearer token which is sent in all API requests.
At the API Gateway level (Apigee), this token is validated.
For backend services, we have a shared Spring Security Auth repository (added via Maven dependency) which uses annotations like @RolesAllowed to enforce role-based access control on individual APIs. This ensures fine-grained authorization.
Q3. How does your project handle service-to-service communication?
Answer: We use both synchronous and asynchronous mechanisms:
- REST APIs for direct service calls (when immediate response is required)
- Apache Kafka for asynchronous event-driven communication (e.g., notifying Payments service after a transaction event)
Q4. Do your microservices share databases or have separate databases?
Answer: We follow a hybrid approach:
- Some services have separate databases (ideal microservices pattern for loose coupling)
- Some services share a common database (practical compromise due to legacy systems)
We use both Oracle (relational) and MongoDB (NoSQL) depending on the service’s requirement.
Q5. How do you ensure scalability and high availability of services?
Answer: We deploy all microservices on Kubernetes (Azure Red Hat OpenShift). We configure replicaCounts in GitOps repo to scale services horizontally by increasing pods. If load increases, we simply update the replica count, and Kubernetes deploys more pods. Apigee handles load balancing between them.
Q6. How does your CI/CD pipeline work for microservices deployment?
Answer: We use a GitOps-based CI/CD pipeline:
- Code changes trigger a build pipeline.
- A Docker image is built and pushed to Docker Artifactory.
- GitOps repo is updated with the new image tag.
- Kubernetes automatically pulls the new image and deploys it.
This ensures automated, consistent deployments.
Q7. How do you monitor and debug your microservices in production?
Answer: We use Elastic Stack (ELK) for centralized logging. All logs from different services and Kubernetes pods are forwarded to ElasticSearch for searching and analysis. We also check Azure OpenShift pod logs for real-time debugging.
Q8. How is API documentation managed in your project?
Answer: All backend APIs are documented using Swagger / OpenAPI specifications. This helps both internal and external developers to understand and consume the APIs easily.
Q9. How do you handle failures and retries in your microservices communication?
Answer:
- For REST APIs, we implement retry mechanisms with exponential backoff and circuit breakers using libraries like Resilience4J or Spring Retry.
- For Kafka, failed messages are handled using dead letter queues (DLQ) so that failed events can be retried or analysed later.
Q10. How does your project ensure secure communication between microservices?
Answer:
- All service-to-service calls use HTTPS for encrypted communication.
- Kafka communication is secured via SSL and authentication (SASL).
- API Gateway (Apigee) and backend services validate Bearer tokens and enforce role-based access via Spring Security.
Q11. How do you manage configuration across environments in microservices?
Answer: We use GitOps repositories to maintain Kubernetes YAML files per environment. Configurations like replica counts, Docker image tags, environment-specific variables are managed through these YAMLs. Secrets (like DB passwords) are managed using Kubernetes Secrets.
Q12. How does your project handle schema changes when services share a database?
Answer: We carefully coordinate schema changes by:
- Using backward-compatible changes (adding columns, not dropping)
- Managing DB migrations via Liquibase/Flyway
- Communicating clearly with teams when schema changes affect multiple services
Whenever possible, we prefer separate databases to avoid this complexity.
Q13. What is the role of Axway in your architecture?
Answer: Axway acts as an API validation and policy enforcement layer. It validates incoming API requests, enforces policies, and returns meaningful errors if an API is not configured properly. This adds an extra layer of governance and robustness before requests reach backend services.
Q14. What challenges have you faced working in microservices architecture?
Answer: Some challenges include:
- Distributed transactions when multiple services need to update data together (we mitigate using eventual consistency and compensating transactions)
- Debugging across services (we mitigate using centralized logging via Elastic and correlation IDs)
- Schema management for shared databases (we mitigate via cautious DB changes and clear communication)
- Service discovery and versioning (we mitigate via Apigee Gateway and clear versioned APIs)
Q15. How do you ensure backward compatibility when updating services?
Answer: We follow API versioning and ensure that new changes are backward compatible. Old consumers can continue using v1 APIs while new features are added to v2 APIs. We test both old and new API versions thoroughly before deployment.
✅ How to use this?
→ Practice these answers in your own words but keep all the technical depth → Be ready to give real project examples (like I’ve shown) → Interviewers want both concept clarity + real-world experience = You’ll stand out
Excellent — here’s both: ① 5 super advanced microservices interview questions (with model answers based on your project) ② System Design questions (with hints to answer confidently)
① 5 Super Advanced Microservices Interview Q\&A (Architect Level)
Q16. How do you manage data consistency across microservices in your project?
Answer: We primarily follow eventual consistency. When multiple services need to update related data, we use Kafka events to propagate state changes asynchronously.
For example, when a payment is successful, Payments service publishes an event to Kafka. Accounts service consumes this event and updates account balances. We avoid distributed transactions to reduce coupling and instead design with idempotent operations and compensating transactions where necessary.
Q17. How does your project ensure observability in a distributed microservices architecture?
Answer: We ensure observability via:
- Centralized Logging: All services log to ElasticSearch for search and visualization.
- Tracing (if asked, mention future-proofing): We are evaluating distributed tracing solutions (like OpenTelemetry or Jaeger) to trace requests across services end-to-end.
- Metrics: Kubernetes gives pod-level metrics. We plan to enhance with Prometheus + Grafana in the future for application-level metrics.
We also use correlation IDs in logs to trace a request as it passes through multiple services.
Q18. How do you manage microservices versioning and backward compatibility in your project?
Answer:
We expose versioned APIs (/v1/payments, /v2/payments) behind Apigee API Gateway.
When releasing a new version:
- We maintain old versions for existing consumers.
- We ensure backward compatibility by supporting optional fields, avoiding breaking schema changes.
- Deprecation is done gradually with communication to clients.
For internal service-to-service APIs, we ensure interface backward compatibility and test both old and new consumers before deployment.
Q19. How do you manage secrets and sensitive configurations across microservices?
Answer: We use Kubernetes Secrets to securely manage sensitive data (like DB passwords, API keys).
Secrets are:
- Encrypted at rest (Kubernetes feature)
- Mounted into pods as environment variables or files
- Access-controlled via Kubernetes RBAC (only specific services can access specific secrets)
We avoid hardcoding secrets or checking them into Git repositories.
Q20. How do you ensure fault tolerance and resilience of your microservices?
Answer: We follow multiple strategies:
- Retry and Timeout: All inter-service REST calls have retry logic and timeouts.
- Circuit Breaker: We plan to use Resilience4j for circuit breaker patterns (if a service is down, avoid overloading it).
- Kubernetes Self-healing: Kubernetes automatically restarts failed pods and reschedules them if nodes crash.
- Kafka DLQs: Failed Kafka messages go into Dead Letter Queues for retries or manual intervention.
- Horizontal Scaling: We can scale up pods quickly via Kubernetes
replicaCount.
② System Design Questions (With Approach Hints)
These may be asked to see if you can apply microservices concepts to design.
Q1. Design a payment processing system using microservices (similar to your Payments service)
Approach Hint:
- Services: Payments, Accounts, Notifications
- Communication: REST for Payments-Accounts, Kafka for async events (payment success → notify)
- API Gateway: Apigee to expose APIs securely
- Authentication: Okta + token validation
- Database: Separate DB per service (Payments Oracle, Notifications MongoDB)
- Scalability: Kubernetes scaling
- Logging: Elastic
- Resilience: Retry, DLQ, circuit breaker
Q2. How would you handle schema evolution if Accounts and Payments share a DB table?
Approach Hint:
- Use backward compatible schema changes
- Blue-green deployments or feature toggles to minimize downtime
- Coordinate schema rollout with DB migration tools (Liquibase/Flyway)
- Gradually migrate to separate schemas (ideal future)
Q3. Design a secure service-to-service communication mechanism.
Approach Hint:
- HTTPS between services
- Mutual TLS (optional advanced answer)
- OAuth2 tokens for service-to-service auth (Okta can issue service tokens)
- Use Spring Security for RBAC
- Kubernetes NetworkPolicies (optional) to restrict pod communication
Q4. Design a microservices logging and monitoring architecture.
Approach Hint:
- Elastic Stack (ELK) for centralized logging
- Correlation ID propagation between services
- Prometheus + Grafana (optional advanced monitoring)
- Kibana dashboards for log visualization
- Alerts on errors/timeouts via Elastic or Prometheus AlertManager
Q5. Design a deployment strategy for rolling out a new version of Payments service without downtime.
Approach Hint:
- Use Kubernetes Rolling Update strategy
- Alternatively, do Blue-Green deployment (2 sets of pods, switch traffic)
- Ensure backward compatibility of APIs
- Use health checks to ensure new pods are healthy before switching
- Gradually increase traffic to new version (Canary Deployment — optional)
✅ How to Prepare These
→ For each design Q, mention components, communication, security, scalability, resilience, monitoring, deployment (these 7 pillars — interviewers love that)
📝 Microservices Architecture (Your Project – Interview Summary)
🏛️ Core Architecture
| Component | Tech Stack / Tool |
|---|---|
| Frontend | Angular SPA + Web Components |
| Auth | Okta + OAuth2 (Frontend & Backend) |
| API Gateway | Apigee (Auth + Routing) |
| Backend Services | Spring Boot Microservices |
| Inter-service Communication | REST APIs + Kafka |
| Databases | Oracle + MongoDB (shared + separate) |
| Deployment | Kubernetes + GitOps (ArgoCD or similar) |
| Observability | ElasticSearch + Kibana (Logging), Azure OpenShift logs |
| CI/CD | GitHub → Build → Docker Artifactory → GitOps deploy |
🛠️ Key Patterns in Use
| Feature | Implementation |
|---|---|
| Authentication | Okta tokens (Frontend) → validated by Apigee → backend |
| Authorization | Spring Security (RolesAllowed) |
| API Versioning | Managed in Apigee (/v1/payments, /v2/accounts) |
| Data Consistency | Eventual Consistency (via Kafka) |
| Fault Tolerance | Retry + Kafka DLQ + K8s Self-healing |
| Scalability | K8s replicaCount (pods auto scale) |
| Logging & Monitoring | Elastic + Correlation IDs + K8s logs |
| Secret Management | Kubernetes Secrets |
| Deployment Strategy | Rolling updates via GitOps + Docker tags |
🎯 Killer Interview Phrases (use these confidently)
- “We follow domain-driven design with bounded contexts.”
- “We ensure eventual consistency via Kafka event propagation.”
- “Our observability stack includes Elastic and correlation IDs.”
- “Apigee handles API authentication, throttling, and routing.”
- “We use GitOps for declarative infrastructure management and consistent deployments.”
- “Our services are designed for independent deployability and fault isolation.”
🚀 Advanced Concepts Ready to Mention
✅ Correlation IDs ✅ Kafka DLQ ✅ Kubernetes ReplicaSets & Self-healing ✅ Event-driven architecture ✅ Circuit breaker / Retry (Resilience4j — future ready) ✅ GitOps Deployment flow (Build → Docker Artifactory → GitOps repo → K8s) ✅ Hybrid DB strategy (Oracle + MongoDB)
📝 Microservices Architecture (Your Project – Interview Summary + Design Patterns)
🏛️ Core Architecture
| Component | Tech Stack / Tool |
|---|---|
| Frontend | Angular SPA + Web Components |
| Auth | Okta + OAuth2 (Frontend & Backend) |
| API Gateway | Apigee (Auth + Routing + Rate-limiting) |
| Backend Services | Spring Boot Microservices |
| Inter-service Communication | REST APIs + Kafka (async) |
| Databases | Oracle + MongoDB (shared + separate) |
| Deployment | Kubernetes + GitOps (ArgoCD or similar) |
| Observability | ElasticSearch + Kibana + Azure OpenShift logs |
| CI/CD | GitHub → Build → Docker Artifactory → GitOps deploy |
🛠️ Key Microservices Design Patterns (used / relevant in your project)
| Pattern | Where / How (Your Project Example) |
|---|---|
| API Gateway | Apigee (handles auth, routing, rate limiting) |
| Circuit Breaker | (Optional / Future) — Resilience4j for fault tolerance in REST/Kafka |
| Saga (Orchestration/Choreography) | For distributed transactions (payments + accounts), Kafka-based async updates ensure eventual consistency |
| Event Sourcing | Kafka (events persist history of state change, e.g., payment processed) |
| CQRS (Command Query Responsibility Segregation) | Read-heavy APIs fetch data from cached or denormalized sources (MongoDB) while writes propagate via Kafka |
| Database per service | Some services have dedicated DBs (Oracle / Mongo), some share DB (accounts + payments may share customer data) |
| Bulkhead | Kubernetes pod/resource isolation prevents cascading failures |
| Retry + Timeout + Fallback | REST clients and Kafka producers (using Retry templates / configs) |
| Service Discovery (optional) | Static service discovery (via Apigee configs + Kubernetes DNS) |
| Externalized Configuration | GitOps YAMLs (config maps, secrets) for environments |
🎯 Killer Interview Phrases (use these confidently)
- “We ensure eventual consistency via Kafka event-driven architecture and adopt the Saga pattern for distributed transactions.”
- “Apigee acts as an API Gateway pattern handling authentication, throttling, and routing.”
- “For inter-service reliability, we apply retry mechanisms and are considering circuit breaker pattern with Resilience4j.”
- “Our deployments are immutable, driven by GitOps, ensuring consistency across environments.”
- “We designed services for independent deployability, fault isolation, and scalability using Kubernetes bulkheads and replicas.”
- “We use a hybrid persistence strategy — relational (Oracle) and NoSQL (MongoDB), following Database-per-service pattern where appropriate.”
🚀 Advanced Concepts Ready to Mention
✅ Correlation IDs (for tracing) ✅ Kafka DLQ (Dead Letter Queue) ✅ Kubernetes ReplicaSets & Self-healing ✅ Event-driven architecture (Kafka-based) ✅ Circuit breaker / Retry / Timeout (Resilience4j ready) ✅ GitOps Flow (Build → Docker Artifactory → GitOps → K8s) ✅ Saga pattern (via Kafka for multi-service consistency) ✅ Hybrid DB (Oracle + MongoDB) ✅ Elastic stack for centralized logging
🗣️ Sample Interview Intro (Project Elevator Pitch)
“I work on a microservices-based architecture where our Angular SPA interacts with multiple Spring Boot services exposed via Apigee API Gateway. We leverage Okta for authentication (OAuth2), Kafka for event-driven communication, and a hybrid Oracle-MongoDB strategy for persistence. Our services follow patterns like Saga for distributed transactions, Database-per-service where applicable, and are deployed on Kubernetes using GitOps for seamless CI/CD. We ensure observability through Elastic logs and fault tolerance using retries and pod isolation.”
🎯 Advanced Microservices — Interview Q\&A (Tailored to Your Project)
1️⃣ What is Microservices Architecture? How is it applied in your project?
Microservices architecture breaks a large application into a collection of small, loosely coupled, independently deployable services. Each service has its own functionality, data, and deployability.
In my project: We have independent Spring Boot services like Payments, Accounts, etc., each exposed via Apigee API Gateway. Some have separate DBs (Oracle/MongoDB), and others share DBs depending on the domain requirement. They communicate via REST and Kafka.
2️⃣ How is authentication handled?
We use Okta (OAuth2) for user authentication. The token obtained post-login is passed as a Bearer token to the backend APIs.
Backend:
Apigee validates tokens. APIs enforce roles via Spring Security using a shared Auth service (maven dependency). @RolesAllowed annotations protect endpoints without rewriting auth logic.
3️⃣ How does service-to-service communication work?
Primarily using REST APIs and Kafka (for async).
- Kafka: For publishing events like “Payment Initiated”, “Account Updated” → consumed by relevant services asynchronously (Saga pattern used for distributed transactions).
- REST: For synchronous queries like getting account details.
4️⃣ How do you ensure data consistency across services?
We follow Eventual Consistency via Kafka (Saga pattern).
Example:
Payment → emits PaymentCompleted → Account service consumes event → updates account balance.
5️⃣ What patterns ensure reliability and fault tolerance?
✅ Retry + Timeout in REST and Kafka calls ✅ Circuit Breaker (we plan Resilience4j for flaky services) ✅ Bulkhead: K8s replica isolation prevents cascading failures ✅ ElasticSearch centralized logs + correlation IDs for tracing
6️⃣ How is CI/CD handled?
We follow GitOps for K8s deployments.
- Code pushed → triggers build → Docker image → Docker Artifactory
- GitOps repo updates tag → K8s cluster pulls new image
- Deploy via Helm / K8s manifests
- Configs managed in GitOps YAML (replicaCount, image tag)
7️⃣ Explain API Gateway usage in your project.
Apigee acts as our API Gateway.
✅ Authenticates Bearer tokens ✅ Routes requests to correct microservice (payments/accounts) ✅ Handles rate-limiting, logging, API versioning ✅ Provides developer portal + Swagger docs
8️⃣ Why did you use both Oracle and MongoDB?
Based on data modeling needs:
- Oracle → transactional, relational (e.g., customer info)
- MongoDB → unstructured, scalable reads (e.g., logs, user preferences)
This follows Polyglot Persistence and Database-per-service pattern.
9️⃣ How do you monitor and debug microservices?
✅ ElasticSearch + Kibana → central logging ✅ Azure OpenShift → pod-level logs ✅ Correlation ID → track request flow across services ✅ Apigee Analytics → API usage + latency
🔟 What are the main challenges in microservices you faced?
- Handling distributed transactions → solved via Kafka Saga
- Service discovery → handled statically via Apigee/K8s DNS
- Managing configs & secrets → solved using GitOps + K8s Secrets
- Maintaining observability → Elastic stack + tracing
🛠️ Extra Credit Qs (If you want to shine more)
| Question | Smart Answer (Your Project) |
|---|---|
| How do you version APIs? | Using Apigee route configs (v1, v2 paths) |
| How do you roll back bad deployments? | GitOps revert + redeploy (image tag rollback) |
| How do you secure inter-service comms? | OAuth tokens + mTLS (if applicable) + Spring Security |
| How do you handle large payloads? | Kafka compression + REST pagination |
| How do you test microservices? | Unit, Integration + Postman/Swagger + Contract testing (future) |