Introduction to Rate Limiter
In modern software systems, particularly in distributed architectures, APIs, and cloud-based services, rate limiting is an essential mechanism to control the flow of incoming requests. It ensures that a service is not overwhelmed by excessive traffic, prevents abuse, and helps maintain system stability, security, and fair resource allocation.
A Rate Limiter is a component that restricts the number of requests a user, IP address, or client can make within a specific timeframe. For example, an API might allow 100 requests per minute per user. If a user exceeds this limit, the system either rejects additional requests or delays them.
Why is Rate Limiting Important?
- Prevents System Overload: Protects servers from being overwhelmed by excessive requests.
- Ensures Fair Usage: Distributes resources fairly among users.
- Enhances Security: Prevents DDoS attacks, brute force login attempts, and API abuse.
- Improves Performance: Helps maintain optimal system response times.
- Cost Optimization: Avoids unnecessary computation and reduces infrastructure costs.
Key Design Considerations
When designing a Rate Limiter, we need to consider:
- Limit Scope: Should it be applied per user, IP, or API key?
- Limit Type: Fixed window, sliding window, token bucket, or leaky bucket?
- Storage Mechanism: Where to track request counts (e.g., in-memory store like Redis, database, or distributed cache)?
- Handling Excess Requests: Should extra requests be rejected, queued, or delayed?
