ChatGPT: I have internal APIs, partner APIs, and public APIs spread across cloud and on-prem. What kind of API gateway setup should I consider for auth, routing, rate limiting, and observability?

For a mixed API estate like internal, partner, and public APIs across cloud and on-prem, you usually want a hybrid API gateway architecture rather than a single centralized gateway.

Recommended setup

1) Separate gateway tiers by exposure

Use different policies and possibly different gateway instances for each trust boundary:

• Public APIs

  • Internet-facing gateway
  • Strong auth (OAuth2/OIDC, JWT validation, mTLS for sensitive partners)
  • WAF/DDoS integration
  • Strict rate limiting and quota enforcement
  • API monetization / developer portal if needed

• Partner APIs

  • Partner-dedicated gateway or dedicated route/tenant on the same gateway platform
  • Mutual TLS and/or signed JWTs
  • Contract-based access control
  • Per-partner quotas, burst limits, IP allowlists, and schema validation if possible

• Internal APIs

  • Private gateway or service-mesh-aware ingress
  • Service-to-service auth using mTLS and SPIFFE/SPIRE or workload identities
  • Internal RBAC/ABAC
  • Lighter rate limiting, but still useful for protecting dependencies

2) Use a central control plane, distributed data planes

A common pattern is:

• Central control plane

  • Manages policies, certificates, route definitions, auth config, analytics settings
  • Gives you one place to govern APIs across cloud and on-prem

• Distributed gateways / data planes

  • Deployed close to workloads in each environment
  • Reduces latency and avoids hairpinning traffic through one location
  • Supports resilience if one region/cloud/on-prem site is isolated

This is often the best fit when you have APIs spread across multiple environments.

3) Auth strategy

Use a layered approach:

• External/public

  • OAuth 2.0 / OIDC for user-facing APIs
  • Client credentials for machine access
  • JWT validation at the gateway
  • mTLS for high-trust B2B integrations

• Internal

  • mTLS between services
  • Short-lived tokens, workload identity, or service accounts
  • Propagate identity claims through headers carefully

• Partner

  • Prefer mTLS + OAuth2 client credentials
  • Consider signed requests or JWT client assertions
  • Per-partner claims mapping and authorization policies

4) Routing approach

You’ll likely need a mix of:

• Host/path-based routing for API versioning and tenant separation
• Header-based routing for partner-specific behavior or canary releases
• Geo/region-aware routing if APIs exist in multiple clouds/sites
• Traffic splitting for blue/green or canary deployments

For on-prem + cloud, make sure the gateway supports:

• private connectivity
• DNS/service discovery integration
• failover across environments if desired

5) Rate limiting and quotas

Apply limits at multiple levels:

• Global edge limits to protect the platform
• Per-client/per-app limits for consumers
• Per-partner quotas for contractual enforcement
• Per-route/per-API limits for expensive endpoints
• Burst + sustained limits rather than only one static number

Use distributed counters if gateways are horizontally scaled.

6) Observability

A mature gateway setup should emit:

• Metrics

  • request count, latency, error rates
  • 4xx/5xx by route, consumer, partner, region
  • auth failures, rate-limit hits, backend timeouts

• Logs

  • correlation IDs / trace IDs
  • request metadata, policy decisions, upstream status
  • avoid logging sensitive payloads by default

• Traces

  • propagate OpenTelemetry trace context
  • trace across gateway → service → downstream dependencies

Also consider:

• API analytics dashboards
• SLA/SLO reporting per API and partner
• anomaly detection on traffic patterns

7) Recommended deployment model

A practical pattern is:

• Cloud: managed gateway or gateway cluster per cloud region
• On-prem: gateway cluster near internal services
• Common governance: one control plane for policies, certs, and analytics
• Optional service mesh: for east-west internal traffic, with the gateway handling north-south ingress/egress

8) Good design principles

• Keep the gateway focused on policy enforcement, auth, routing, throttling, and telemetry
• Avoid putting heavy business logic in the gateway
• Use zero-trust assumptions between environments
• Segment public/partner/internal traffic clearly
• Standardize on OpenAPI, OAuth2/OIDC, mTLS, and OpenTelemetry

If you want a concrete target architecture

A strong default would be:

• One API management platform
• Multiple gateway/data-plane deployments
  • public edge gateway
  • partner gateway
  • internal gateway
  • on-prem gateway(s)
• Central control plane
• OIDC/OAuth2 + mTLS
• Distributed rate limiting
• OpenTelemetry-based observability
• Optional service mesh for internal service-to-service traffic

If you want, I can also sketch:

1. a reference architecture diagram in text, or
2. a vendor-neutral feature checklist for evaluating gateway products.