EP 7: How Apps Like Instagram, Facebook Ship Features Without any Downtime

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Table of Contents

• 1. Canary Deployments

• 2. Feature Flags

• 3. Shadow test new backend services

• 4. Blue-Green Deployment

• 5. Build for backward compatibility

• 6. Crazy monitoring

• So how does it all come together?

Ever wondered how Instagram manages to roll out new features without breaking anything, even with millions of people using it at the same time 24/7?

You wake up one morning, open Instagram, and boom there’s a new feature sitting right there in your app. No app crash. No downtime. No annoying "we're updating, please wait" screen. It just, works!

But behind the scenes, there’s a lot going on. Apps like Instagram are always under heavy traffic, people are posting stories, DMing, liking, scrolling, that too 24/7. So how do they release new features without interrupting any of that?

Here’s how they pull it off (and it's actually pretty clever)!

1. Canary Deployments

They don’t release to everyone at once, they do Canary Deployments.

Instagram doesn’t just push code to the entire user base in one go. That’s risky. Instead, they use a canary deployment strategy, where the new feature is first rolled out to a small subset of users (say 1% in a specific region).

They monitor metrics like:

• Error rates (HTTP 500s)

• Latency

• App crashes

• Backend service load

If everything looks clean, they gradually roll it out to more users — 10%, 50%, and so on.

If something explodes? Rollback is easy, and the blast radius is small.

2. Feature Flags

Features are deployed but turned off, thanks to Feature Flags

Instagram engineers ship code behind feature flags (also called toggles). So even though the feature is technically in production, it’s not live until they flip the flag.

They can:

• Enable the feature for internal testing

• Do gradual rollouts (by geography, platform, user type)

• Instantly disable it (kill switch) if bugs pop up

These flags are usually managed by tools like LaunchDarkly, Unleash, or in-house solutions.

3. Shadow test new backend services

This one's slick: Instagram can test new backend services with real production traffic , without users ever seeing the results.

How?

They do shadow testing:
Incoming requests are duplicated and sent to both the current service and the new one. The response from the new system isn’t shown to the user — it’s just logged and compared.

This lets them:

• Measure performance differences

• Detect bugs or inconsistencies

• Prepare for safe cutovers

Think of it as running a new engine next to the current one — just to see if it’s ready to take over.

4. Blue-Green Deployment

Instagram also uses Blue-Green Deployment in their infrastructure.

They maintain two nearly identical production environments:

• Blue = current live system

• Green = new version with the latest code

They:

1. Deploy to Green

2. Run sanity checks, integration tests, and warm it up

3. Switch traffic from Blue to Green (via a load balancer or service mesh like Envoy or Istio)

If Green starts misbehaving? Roll traffic back to Blue immediately.

5. Build for backward compatibility

A huge part of releasing safely is making sure the client (mobile app) and backend APIs can handle different versions at the same time.

Instagram’s backend services are built with:

• Versioned APIs

• Graceful fallbacks

• Schema migrations that don’t break existing data

So even if some users haven’t updated their app yet, things don’t break.

6. Crazy monitoring

Rolling out anything without observability is like flying blind.

Instagram’s infra includes:

• Real-time metrics (via Grafana, Prometheus, or internal tooling)

• Distributed tracing (like OpenTelemetry or Zipkin)

• Alerting systems (on things like p99 latency, CPU spikes, DB locks)

They also run synthetic monitoring to simulate user interactions and catch issues proactively.

And if something does go wrong? Auto-rollbacks and incident workflows kick in fast.

So how does it all come together?

All of this makes their release process:

• Safe

• Scalable

• Invisible to the user

I hope this gives you a clear picture of Caching, Why it is needed and How it is used. Will cover Cache Eviction and Invalidation Strategies in the next blog.

In a nutshell, Instagram rolls out new features without breaking things by deploying code early behind feature flags, testing it quietly using real traffic (shadow testing), and releasing it gradually through canary deployments. They monitor everything in real-time and can instantly disable a feature if something goes wrong. This lets them move fast while keeping the app stable for millions of users.

Keep learning. You’ve got this!