Deployment

Feature flags turn deployment into a two-step process: ship the code, then enable the feature. This separation is powerful when done right and a maintenance nightmare when done wrong. The Core Value Proposition Without feature flags, deployment equals release. Ship broken code? Users see it immediately. Need to roll back? Redeploy the previous version. Want to test with 1% of users? Build custom infrastructure. With feature flags, you decouple these concerns: ...

Blue-green deployment is one of those patterns that sounds simple until you try to implement it at scale. Here’s what actually works. The Core Concept You maintain two identical production environments: Blue (current) and Green (new). Traffic flows to Blue while you deploy and test on Green. When ready, you flip traffic to Green. If something breaks, flip back to Blue. Simple in theory. Let’s talk about the messy reality. ...

Deployment and release are not the same thing. Feature flags let you deploy code to production without releasing it to users. Here’s how to implement them without creating technical debt. Why Feature Flags? W D W D i e i e t p t p h l h l o o o P u y f y r t l o = a → b f g l l R s T ↓ e a e : e m g l s s s e t ? : a s i I e n n s = p t r a R o n i d t s k → d i G s r a a b d l u e a l ( n r o o l r l o o l u l t b a → c k F u n l e l e d r e e d l ) e a s e Use cases: ...

Docker Compose isn’t just for development. With the right patterns, it’s a legitimate production deployment tool for small-to-medium workloads. Here’s how to do it without the footguns. Base Structure 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 # docker-compose.yml version: "3.8" services: app: image: myapp:${VERSION:-latest} restart: unless-stopped environment: - NODE_ENV=production deploy: resources: limits: cpus: '2' memory: 1G healthcheck: test: ["CMD", "curl", "-f", "http://localhost:3000/health"] interval: 30s timeout: 10s retries: 3 start_period: 40s Key elements: ...

Schema changes are scary. One bad migration can take down your entire application. Here’s how to evolve your database safely, even with users actively hitting it. The Core Problem You need to rename a column. Sounds simple: 1 ALTER TABLE users RENAME COLUMN name TO full_name; But your application is running. The moment this executes: Old code looking for name breaks New code looking for full_name also breaks (until deploy finishes) You have a window of guaranteed failures This is why database migrations need careful choreography. ...

Feature flags seem simple: wrap code in an if statement, flip a boolean, ship whenever you want. In practice, they’re one of the fastest ways to accumulate invisible technical debt. Here’s how to get the benefits without the baggage. Why Feature Flags Matter The core value proposition is decoupling deployment from release: 1 2 3 4 5 6 7 8 9 10 11 12 # Without flags: deploy = release def checkout(): process_payment() send_confirmation() # With flags: deploy when ready, release when confident def checkout(): process_payment() if feature_enabled("new_confirmation_flow"): send_rich_confirmation() else: send_confirmation() This separation enables: ...

A good CI/CD pipeline catches bugs early, deploys reliably, and gets out of your way. A bad one is slow, flaky, and becomes the team’s bottleneck. Let’s build a good one. Pipeline Stages A typical pipeline flows through these stages: C o m m i t → B u i l d → T e s t → S e c u r i t y S c a n → D e p l o y S t a g i n g → D e p l o y P r o d Each stage gates the next. Fail early, fail fast. ...

Deploying shouldn’t mean downtime. Blue-green deployment lets you release new versions instantly and roll back just as fast. The Concept You maintain two identical production environments: Blue: Currently serving live traffic Green: Idle, ready for the next version To deploy: Deploy new version to Green Test Green thoroughly Switch traffic from Blue to Green Green is now live; Blue becomes idle Next deploy: repeat with roles reversed B A e f f U t U o s e s r e r e e r r s s s d w e → i → p t l L c L o o h o y a : a : d d B B a a l l a a n n c c e e r r → → [ [ [ [ B G B G l r l r u e u e e e e e n n v ] v 1 1 v . i . 1 0 d 0 . ] l ] 1 e ] ✓ i d ✓ L l I e L V I E V E Implementation with Nginx Simple traffic switching with upstream blocks: ...

Deploying code and releasing features are not the same thing. Treating them as identical creates unnecessary risk, slows down development, and makes rollbacks painful. Feature flags fix this. The Problem with Deploy-Equals-Release Traditional deployment pipelines work like this: code merges, tests pass, artifact builds, deployment happens, users see the change. It’s linear and fragile. What happens when the feature works in staging but breaks in production? You roll back the entire deployment, potentially reverting unrelated fixes. What if you want to release to 5% of users first? You can’t — it’s all or nothing. ...

Database migrations are where deploys go to die. Here’s how to make them safe. The Golden Rule Every migration must be backward compatible. Your old code will run alongside the new schema during deployment. If it can’t, you’ll have downtime. Safe Operations These are always safe: Adding a nullable column Adding a table Adding an index (with CONCURRENTLY) Adding a constraint (as NOT VALID, then validate later) Dangerous Operations These need careful handling: ...