What is Rate Limiting?

Rate limiting is a technique used to control the rate of requests that clients can make to an API or service. It protects against abuse, ensures fair usage, maintains service stability, and manages costs.

Why Rate Limit?

Security

Prevent brute force attacks
Block credential stuffing
Mitigate DDoS
Stop scraping

Stability

Protect backend systems
Ensure availability
Manage load

Business

Enforce usage tiers
Control costs
Fair resource sharing

Rate Limiting Strategies

Fixed Window

X requests per time window
Simple to implement
Burst at window boundaries

Sliding Window

Smooth request distribution
More complex
Better protection

Token Bucket

Allows controlled bursts
Refills over time
Flexible

Leaky Bucket

Constant output rate
Queues excess requests
Smooths traffic

Implementation Levels

Application Per-endpoint limits.

User/API Key Per-account limits.

IP Address Per-source limits.

Global Total service capacity.

Response Handling

HTTP 429 Too Many Requests.

Retry-After Header When to retry.

X-RateLimit Headers

X-RateLimit-Limit
X-RateLimit-Remaining
X-RateLimit-Reset

Best Practices

Use multiple strategies
Communicate limits clearly
Provide rate limit headers
Allow reasonable bursts
Consider tiered limits