Do I need API gateway policies if my services already handle auth?

Not always—but often yes, depending on what you want the gateway to do.

Short answer

If your services already handle authentication and authorization, you don’t strictly need API gateway policies for auth. But gateway policies can still add value by enforcing cross-cutting controls before requests reach your services.

When you can skip gateway auth policies

You may not need them if:

• Each service fully validates auth itself
• You’re fine with every service independently handling tokens/claims
• The gateway is only doing routing/load balancing
• You want to avoid duplicated policy logic

Why gateway policies are still useful

Gateway policies are helpful for:

• Early rejection of unauthenticated/invalid requests
• Centralized enforcement of shared rules
• Rate limiting / quotas
• IP allow/deny lists
• Request/response transformation
• Header injection or normalization
• Logging, tracing, and correlation IDs
• Basic protection before traffic hits downstream services

Common best practice

A common pattern is:

• Gateway: coarse-grained checks
  • valid token format
  • required auth header present
  • rate limits
  • tenant/header checks
• Services: fine-grained authorization
  • user can access this specific resource
  • role/scope/ownership checks

This gives you defense in depth and keeps services from being flooded with obviously bad requests.

Important caveat

If the gateway is doing auth, make sure:

• Services don’t blindly trust headers from the gateway unless internal network trust is enforced
• JWTs or identity context are validated or signed
• You have a clear trust boundary

Rule of thumb

• AuthN/AuthZ already in services? Gateway auth policies are optional.
• Need central control, consistency, or protection? Gateway policies are worth it.

If you want, I can also help you decide this for a specific setup like Kong / Apigee / Azure API Management / AWS API Gateway / NGINX.