When you start building systems on AWS, Cognito looks like the perfect choice for managed authentication:

• Fully hosted user management
• Secure, standards-based (OAuth2, OIDC, SAML)
• Tight integration with the AWS ecosystem

But when I began designing a multi-region architecture, I ran into one of Cognito’s biggest limitations:

🚫 Cognito User Pools are region-bound.

• No cross-region replication
• No native failover
• Users are tied to the region where they sign up

So if a user creates an account in us-east-1, they won’t exist in eu-west-1. And that’s a deal-breaker for many global architectures.

Why This Matters

This limitation shows up in real-world scenarios:

• 🌍 Active-active deployments: serving traffic from multiple regions for low latency
• 🛡️ Resilience & DR: needing to fail over cleanly without losing user identities
• ⚖️ Compliance: storing user data in-region (e.g., GDPR, data sovereignty)
• ✈️ Roaming users: customers who travel and expect seamless logins globally

At first, I thought I was missing a hidden setting or replication option. But after deep research, I confirmed: Cognito doesn’t support it out of the box.

Common Approaches

When faced with this, you’ve got a few architectural options. Each has trade-offs:

1. Single Region with Global Access

• Pick one region (e.g., us-east-1) and keep all Cognito users there.
• Use Route 53 latency-based routing + CloudFront to reduce access impact.

Pros:
✅ Simpler setup
✅ Full feature parity with Cognito

Cons:
❌ Higher latency for distant regions
❌ Region outage = global outage

2. Multiple Pools + Federation

• Create a user pool per region.
• Use Cognito Identity Federation or a custom IdP to link accounts.

Pros:
✅ Regional data compliance
✅ Users authenticate closer to them

Cons:
❌ Complex federation logic
❌ Syncing attributes & passwords is tricky
❌ Adds login flow complexity

3. External Identity Provider (IdP)

• Use a global IdP like Auth0, Okta, or Azure AD B2C.
• Cognito becomes optional — or is bypassed completely.

Pros:
✅ Mature, global IdPs handle replication
✅ Richer auth features

Cons:
❌ Extra cost
❌ Less AWS-native integration

4. Custom Authentication Layer

• Build your own authentication service on top of DynamoDB Global Tables (or Aurora Global Database).
• Store user identities in a replicated datastore and handle auth logic yourself.

Pros:
✅ Full control
✅ Native global replication
✅ Can align with business-specific needs

Cons:
❌ You own the complexity (tokens, password resets, MFA, security)
❌ Higher maintenance overhead

My Approach

In my case, I needed active-active multi-region deployments for resilience and latency.
I ended up building custom authentication backed by DynamoDB Global Tables:

• Global user table replicated across regions
• Lambda functions for login, signup, token issuance
• API Gateway as the front door
• Custom logic for MFA and password reset

This gave me full control and seamless user experience across regions.
But I also had to own the complexity that Cognito usually abstracts away.

Lessons Learned

• Cognito is great for single-region or simpler architectures.
• For multi-region: you must choose between complexity, cost, and control.
• Don’t assume AWS services are multi-region by default — many are region-scoped.

Final Thoughts

Cognito’s region-bound design is a gotcha for teams planning multi-region systems.

If you’re starting fresh:

• For simplicity → single pool, global access
• For compliance or low latency → multi-pool federation or external IdP
• For maximum control → custom auth service

💬 I’d love to hear your take.
Have you solved Cognito’s multi-region challenge differently? Would you stick with Cognito, federate, or ditch it altogether?