Solve: Multi-Region DB Latency and Compliance on AWS

Solving Multi-Region DB Latency and Compliance on AWS

Problem

A Y Combinator–stage startup is using a single AWS-hosted relational database but experiencing performance issues from users in other regions. Worse yet, compliance regulations prohibit data from crossing regional boundaries. They want low latency, minimal complexity, and strong data residency.

Clarifying the Issue

The challenge lies in designing a multi-region relational database architecture that:

• Keeps user data inside its region (compliance)
• Reduces cross-region latency (performance)
• Doesn’t require running and syncing separate databases per region (complexity)

They considered Aurora DSQL and asked for advice in an AWS Slack community.

Why It Matters

As global apps scale, data locality becomes critical. Regulatory frameworks like GDPR, HIPAA, and country-specific rules (e.g., India’s Data Protection Act) force architects to rethink traditional database patterns.

Startups can’t afford bloated ops teams or custom replication strategies — they need a solution that just works without compromising on compliance or speed.

Key Terms

• Aurora DSQL: AWS’s serverless-compatible version of Aurora with SQL interface, designed for simplified ops.
• Read Replica: A read-only copy of a DB in another region, not write-safe, and not suitable if data must not leave region.
• Sharding: Splitting data across DBs or tables; in this case, by geographic region.
• Geo-partitioned SQL: Distributed databases (e.g., YugabyteDB, CockroachDB) that allow pinning data to specific regions at a row or table level.

Steps at a Glance

1. Start with Aurora DSQL — treat each region as a shard.
2. Implement routing logic in the app layer to direct users to the correct regional DB.
3. Scale up later using geo-partitioned SQL for more control over compliance and distribution.

Detailed Steps

Step 1: Deploy Aurora DSQL in Each Region

Spin up Aurora DSQL clusters per geographic region. Each cluster is logically separate but treated as a shard of the larger application.

You might name clusters like:

• aurora-us-east
• aurora-eu-west
• aurora-ap-south

Then, manage connections with something like this in your config: 

json

{
  "us-east-1": "aurora-us-east.cluster-abc123.us-east-1.rds.amazonaws.com",
  "eu-west-1": "aurora-eu-west.cluster-xyz456.eu-west-1.rds.amazonaws.com"
}

Step 2: Implement App-Layer Routing

Update the application to detect user location (via IP or account metadata) and route them to the correct regional Aurora instance. This keeps reads/writes in-region.

Here’s an example in Node.js (Express-style): 

js

const dbMap = {
  'us-east-1': getAuroraClient('us-east-1'),
  'eu-west-1': getAuroraClient('eu-west-1'),
};

function detectRegion(ip) {
  // Dummy logic — in real world, use IP geolocation
  return ip.startsWith('192.') ? 'us-east-1' : 'eu-west-1';
}

app.use((req, res, next) => {
  const region = detectRegion(req.ip);
  req.db = dbMap[region];
  next();
});

app.post('/signup', async (req, res) => {
  const user = await req.db.insertUser(req.body);
  res.json(user);
});

🛠️ Bonus: If you store user metadata (e.g., country or preferred region) in a JWT or session, you can skip IP lookups and route directly.

Step 3: Handle Cross-Shard Metadata (Optional)

For global settings (like feature flags, UI config), use an S3 bucket with CloudFront or a shared config DB that's read-only across shards.

Example config fetch: 

js

const config = await s3.getObject({ Bucket: 'my-global-config', Key: 'app-settings.json' });

Step 4: Upgrade to Geo-Partitioned SQL When Ready

If tighter controls are needed (e.g., per-row residency, distributed transactions), migrate to a database like YugabyteDB or CockroachDB.

These allow data residency at the row or table level: 

sql

CREATE TABLE users (
  id UUID PRIMARY KEY,
  name TEXT,
  region STRING NOT NULL
) PARTITION BY LIST (region);

ALTER PARTITION us_east OF users CONFIGURE ZONE USING
  constraints = '[+region=us-east1]';

This setup ensures that even within a distributed cluster, your data stays where it belongs.

Conclusion

This real-world Slack thread distilled the modern multi-region DB dilemma perfectly: how do you balance compliance, performance, and simplicity?

✅ Aurora DSQL with regional sharding is a great starting point — low ops, easy entry.
✅ Geo-partitioned SQL systems like YugabyteDB or CockroachDB offer a smooth path forward when the need for control increases.

The key takeaway: start small, scale smart, and keep the user’s data close to home.

* * * 

Aaron Rose is a software engineer and technology writer.