Multi-Region Deployment Case Study

Latency goals, data residency, and failover drills across EU and US. The team prioritized operational ownership while migrating on a Nestlancer-style stack—gateway at the edge, domain NestJS services, Prisma on Postgres, async work through RabbitMQ, and media on Backblaze B2.

Where we started

The team inherited single-region Postgres with freelancers uploading globally. The triggering incident was clear: APAC upload failures when US-East media workers saturated. Leadership funded the refactor when customer-visible latency and support load rose together—not when the diagram looked messy.

Architecture before

• Single deploy artifact coupling unrelated domains
• Synchronous cross-module HTTP with partial timeouts
• Mixed read/write traffic on one database primary
• Ad-hoc file storage complicating virus scan and CDN caching

Migration timeline

Discovery

Mapped single-region Postgres with freelancers uploading globally and inventoried which routes could move behind the gateway without user-visible changes.

Strangler cutover

Routed new traffic through NestJS handlers while legacy paths drained over 3 weeks.

Reliability hardening

Added Backblaze B2, gateway, RabbitMQ with explicit SLOs owned by a 9-engineer platform squad.

Stabilize and learn

Ran game days for DLQ replay, replica lag failover, and presigned upload expiry edge cases.

Patterns we applied

• Backblaze B2 presigned uploads moved bytes off API pods; workers handled thumbnails.
• API gateway centralized auth, OpenAPI, and aggregation for mobile clients.
• RabbitMQ workers absorbed notification and indexing fanout with DLQ replay runbooks.

Code sketch from the cutover

@Controller('blog')
export class BlogGatewayController {
  constructor(private readonly blogClient: BlogServiceClient) {}

  @Get('posts')
  list(@Query() query: ListPostsDto) {
    return this.blogClient.listPosts(query);
  }
}

Results

• regional upload URLs and workers cut failed uploads 61%
• On-call pages for queue backlog fell after outbox lag dashboards went live
• Product teams could ship blog and portfolio changes without redeploying payments
• Support tickets citing 'stale listings' dropped once read paths moved to replicas

Retrospective checklist

• Game day DLQ replay documented with ordering notes
• Replica lag runbook tested in staging monthly
• Presigned upload TTL aligned with mobile retry policy
• Gateway error envelope consistent across all domain services
• Post-incident templates link to dashboards—not screenshots

Lesson

Microservices did not arrive on day one. The team earned splits by proving operational ownership per domain—not by copying a reference diagram. The Nestlancer patterns above were adopted only after metrics justified the coordination cost.