🛠️ Six Pillars of System Design

  1. Requirements & Constraints

    • Define what the system must do (functional requirements) and limits (budget, tech stack, latency, legal).
    • Example: “Support 1 million users, respond within 200ms.”

  2. High-Level Architecture

    • Decide the overall structure of the system.
    • Includes components, modules, services, and how they interact.
    • Example: Client → API Gateway → Microservices → Database

  3. Scaling & Performance

    • Plan for handling growth in traffic and data.
    • Consider horizontal vs vertical scaling, caching, load balancing, concurrency.
    • Example: Add Redis caching, database sharding, or CDNs for performance.

  4. Data Storage Strategy

    • Choose how and where to store data: SQL, NoSQL, columnar, or object storage.
    • Decide partitioning, replication, backup, and retention policies.

  5. Security & Authentication

    • Protect data and system access.
    • Include authentication, authorization, encryption, secrets management, and auditing.

  6. Monitoring & Reliability

    • Ensure system health, availability, and fault tolerance.
    • Include logging, metrics, alerts, retries, failover, and SLA/SLO tracking.

💡 Analogy: Designing a system is like building a secure, scalable, and reliable city: