How do I control API traffic with throttling and routing?

To control API traffic, you usually combine throttling (limit how much traffic is allowed) and routing (decide where traffic should go).

1) Throttling: limit request volume

Throttling protects your API from overload and abuse.

Common throttling strategies

• Rate limiting: allow, for example, 100 requests per minute per user/API key/IP.
• Burst control: allow short spikes but cap sustained traffic.
• Concurrency limits: cap the number of simultaneous requests.
• Quota limits: enforce daily/monthly usage caps.

Typical responses

• HTTP 429 Too Many Requests
• Include headers like:
  • Retry-After
  • X-RateLimit-Limit
  • X-RateLimit-Remaining
  • X-RateLimit-Reset

Where to enforce throttling

• API gateway: best common place
• Reverse proxy: NGINX, Envoy, HAProxy
• Application layer: useful for user-specific logic
• WAF/CDN: for edge protection

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2) Routing: direct traffic to the right backend

Routing controls which service/version/region handles the request.

Common routing approaches

• Path-based routing
  • /v1/* → service A
  • /v2/* → service B
• Host-based routing
  • api.example.com → public API
  • internal-api.example.com → internal service
• Header-based routing
  • route by X-Tenant-ID, X-Canary, or auth claims
• Weighted routing
  • 90% to stable version, 10% to new version
• Geo/region routing
  • send users to nearest region
• Failover routing
  • redirect to backup service if primary fails

Routing goals

• load balancing
• canary releases
• blue/green deployments
• multi-tenant isolation
• regional compliance/performance

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3) Combine throttling + routing

A typical flow:

1. Client sends request
2. Gateway authenticates
3. Throttle check based on API key/user/IP/tenant
4. Route selection based on path/host/header/weight/region
5. Forward to backend
6. Return response

This lets you:

• protect backends from overload
• keep noisy tenants from dominating capacity
• send premium customers to higher-priority routes
• safely roll out new versions

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4) Example patterns

Example A: per-user throttling + path routing

• /public/*: 1000 req/min per IP
• /admin/*: 100 req/min per user, stricter auth
• /v2/*: 10% of traffic to new service

Example B: tenant-aware routing

• Tenant A gets routed to cluster A
• Tenant B gets routed to cluster B
• Each tenant gets its own rate limit and quota

Example C: priority routing

• Gold customers:
  • higher rate limits
  • preferred backend pool
• Free tier:
  • lower rate limits
  • queue or reject when overloaded

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5) Implementation options

In an API gateway

Use policies such as:

• rate limiting
• quota
• JWT/API key validation
• route rules
• retries/timeouts/circuit breakers

Examples:

• Kong
• Apigee
• AWS API Gateway
• Azure API Management
• NGINX / Envoy / Traefik

In code

Use middleware/interceptors:

• token bucket or leaky bucket rate limiter
• route lookup table
• tenant/user identification from auth token

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6) Best practices

• Throttle by identity, not just IP, when possible
• Return 429 with clear retry guidance
• Log limit hits for tuning
• Use burst + sustained limits together
• Separate limits by route, tenant, and environment
• Add timeouts, retries, and circuit breakers alongside routing
• Test with realistic traffic patterns

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If you want, I can show you:

1. a generic architecture diagram,
2. an NGINX/Envoy example, or
3. a code sample for rate limiting and routing.