Do I need an API gateway for routing by region or tenant?

Not always.

You need an API gateway for region- or tenant-based routing only if that routing logic needs to happen centrally and consistently across many clients or services. Otherwise, you may be better off with simpler options.

Use an API gateway if:

• Clients shouldn’t know about backend topology
  • The gateway can route requests to the right region or tenant backend transparently.
• You need shared cross-cutting features
  • Auth, rate limiting, logging, request transformation, tenant isolation, WAF, retries, etc.
• Routing rules are complex or frequently changing
  • Example: tenant A -> us-east, tenant B -> eu-west, with failover and versioning.
• You want one enforcement point
  • Helpful for governance and security, especially in multi-tenant systems.
• You have many apps/services
  • Avoid duplicating routing logic everywhere.

You may not need one if:

• The routing is simple
  • e.g. DNS, geo-DNS, or a basic load balancer can handle region selection.
• Tenant routing is already handled at another layer
  • For example, inside the application after auth, or via database sharding.
• You only have a few services or clients
  • Direct service discovery or ingress routing may be enough.
• Latency and operational simplicity matter more
  • A gateway adds another hop and another system to run.

Common alternatives

• DNS / GeoDNS / traffic manager for region routing
• Load balancer / ingress controller for basic path/host routing
• Service mesh for service-to-service traffic and policy
• Application-level routing when tenant context is part of business logic
• CDN / edge router for location-based steering at the edge

Rule of thumb

• Region routing: start with DNS/GeoDNS or traffic manager
• Tenant routing: use an API gateway if tenant isolation/policy/routing must be centralized; otherwise handle it in the app or service mesh

If you want, I can help you decide based on your setup (cloud, number of tenants, active-active regions, auth model, etc.).