Do I need an API gateway for internal services?

Not always.

For internal services, an API gateway is useful when you need one or more of these:

• Centralized auth: one place to verify tokens, mTLS, service-to-service policies
• Routing / traffic control: path-based routing, versioning, canary releases
• Rate limiting / quotas: prevent noisy neighbors or abuse
• Observability: consistent logging, tracing, metrics
• Protocol translation: e.g. HTTP to gRPC
• Unified policy enforcement: retries, headers, CORS, request shaping
• A stable front door: hide service topology from clients

You may not need one if:

• Services are only called within a trusted network
• You already have service mesh or sidecar-based controls
• The number of services is small and simple
• You want to avoid extra latency, complexity, and operational overhead
• Clients are other backend services that can talk directly via DNS/service discovery

Rule of thumb

• Small/internal monolith-to-services setup: probably skip the gateway
• Many services + multiple teams + shared cross-cutting concerns: gateway can help a lot
• Service-to-service traffic inside Kubernetes/cloud: consider service mesh first if your main need is security/observability rather than edge API management

Common pattern

Use:

• Gateway at the edge for external clients
• Direct service-to-service calls internally
• Add service mesh if you need internal traffic policy and telemetry

If you want, I can help you decide based on your setup (Kubernetes, number of services, auth model, traffic patterns, etc.).