How do I enforce auth and rate limits across all my APIs from one place?

Use an API gateway or API management platform as the central enforcement point.

What it gives you

Put a gateway in front of all your services so it can handle, in one place:

• Authentication: verify JWTs, API keys, OAuth tokens, mTLS, etc.
• Authorization: route based on roles/scopes/claims
• Rate limiting / quotas: per user, per key, per IP, per route, per tenant
• IP allow/deny lists
• Request validation / transformation
• Logging / metrics / tracing
• CORS / TLS termination

Typical setup

Clients → API Gateway → backend services

The gateway becomes the single policy enforcement layer, so each service doesn’t need to reimplement the same auth and throttling logic.

Common options

• Open source: Kong, Tyk, KrakenD, Envoy, Traefik, NGINX
• Cloud-managed: AWS API Gateway, Azure API Management, Apigee, Cloudflare API Gateway
• Service mesh (internal traffic): Istio, Linkerd, Consul, Envoy-based meshes

Recommended approach

• Use the gateway for edge APIs exposed to clients.
• Use a service mesh or internal gateway for service-to-service controls if needed.
• Keep business authorization in the app where it depends on domain rules; use the gateway for coarse-grained enforcement.

Example policy model

• Require a valid JWT on every request
• Rate limit:
  • 100 req/min per API key
  • 1,000 req/min per tenant
  • stricter limits on /login and /otp
• Block unknown IP ranges
• Add audit logs and correlation IDs

Important caveat

A gateway is great for centralized enforcement, but don’t rely on it for everything:

• Keep sensitive authorization checks in services too
• Don’t make the gateway a single point of failure without redundancy
• Cache carefully and design for failover

If you want, I can recommend the best option for your stack (AWS, Kubernetes, .NET, Node, Python, etc.) and sketch a concrete setup.