“Throttling per user / IP / API key” refers to a rate-limiting mechanism used in APIs and backend systems to control how many requests a client can make in a given time window.
🔹 Why Throttling?
Without throttling:
- A single user or buggy client could flood your system with requests.
- This can cause server overload, higher costs, or denial of service for others.
With throttling:
- You protect backend resources.
- Ensure fair usage (no single client hogs all capacity).
- Improve security (limit brute-force attacks).
🔹 Per User / IP / API Key Meaning
-
Per User 👤
- Each authenticated user has a request quota.
- Example: User A can make 100 requests per minute, User B can make 200 requests per minute.
-
Per IP Address 🌐
- Requests are limited by client IP address.
- Example: Only 50 requests per second from a single IP.
- Common for unauthenticated APIs.
-
Per API Key 🔑
- If clients use API keys, each key has its own quota.
- Example: API Key X gets 1000 requests/day, API Key Y gets 500 requests/day.
🔹 Example in Practice
Suppose you run an API:
GET /api/v1/products
You might enforce throttling like:
- Per user: 100 requests/minute.
- Per IP: 50 requests/sec.
- Per API key: 1000 requests/day.
So:
- If a user exceeds 100 requests/minute → they get
429 Too Many Requests. - If one IP floods you → throttling kicks in.
- If an API key crosses daily quota → requests are blocked until reset.
🔹 How It’s Implemented
Common algorithms for throttling:
- Token Bucket – Tokens replenish at fixed rate; each request consumes one.
- Leaky Bucket – Requests processed at steady rate; excess requests dropped.
- Fixed Window – Count requests in fixed intervals (e.g., per minute).
- Sliding Window – More accurate distribution by checking moving time window.
👉 In short: Throttling per user/IP/API key means your system enforces request rate limits individually for each user, IP address, or API key to ensure fair and safe usage.