Deployment Patterns

Production deployment workflows and CI/CD best practices.

When to Activate

• Setting up CI/CD pipelines
• Dockerizing an application
• Planning deployment strategy (blue-green, canary, rolling)
• Implementing health checks and readiness probes
• Preparing for a production release
• Configuring environment-specific settings

Deployment Strategies

Rolling Deployment (Default)

Replace instances gradually — old and new versions run simultaneously during rollout.

Instance 1: v1 → v2  (update first)
Instance 2: v1        (still running v1)
Instance 3: v1        (still running v1)

Instance 1: v2
Instance 2: v1 → v2  (update second)
Instance 3: v1

Instance 1: v2
Instance 2: v2
Instance 3: v1 → v2  (update last)

Pros: Zero downtime, gradual rollout Cons: Two versions run simultaneously — requires backward-compatible changes Use when: Standard deployments, backward-compatible changes

Blue-Green Deployment

Run two identical environments. Switch traffic atomically.

Blue  (v1) ← traffic
Green (v2)   idle, running new version

# After verification:
Blue  (v1)   idle (becomes standby)
Green (v2) ← traffic

Pros: Instant rollback (switch back to blue), clean cutover Cons: Requires 2x infrastructure during deployment Use when: Critical services, zero-tolerance for issues

Canary Deployment

Route a small percentage of traffic to the new version first.

v1: 95% of traffic
v2:  5% of traffic  (canary)

# If metrics look good:
v1: 50% of traffic
v2: 50% of traffic

# Final:
v2: 100% of traffic

Pros: Catches issues with real traffic before full rollout Cons: Requires traffic splitting infrastructure, monitoring Use when: High-traffic services, risky changes, feature flags

Docker

Multi-Stage Dockerfile (Node.js)

dockerfile
1# Stage 1: Install dependencies
2FROM node:22-alpine AS deps
3WORKDIR /app
4COPY package.json package-lock.json ./
5RUN npm ci --production=false
6
7# Stage 2: Build
8FROM node:22-alpine AS builder
9WORKDIR /app
10COPY --from=deps /app/node_modules ./node_modules
11COPY . .
12RUN npm run build
13RUN npm prune --production
14
15# Stage 3: Production image
16FROM node:22-alpine AS runner
17WORKDIR /app
18
19RUN addgroup -g 1001 -S appgroup && adduser -S appuser -u 1001
20USER appuser
21
22COPY --from=builder --chown=appuser:appgroup /app/node_modules ./node_modules
23COPY --from=builder --chown=appuser:appgroup /app/dist ./dist
24COPY --from=builder --chown=appuser:appgroup /app/package.json ./
25
26ENV NODE_ENV=production
27EXPOSE 3000
28
29HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
30  CMD wget --no-verbose --tries=1 --spider http://localhost:3000/health || exit 1
31
32CMD ["node", "dist/server.js"]

Multi-Stage Dockerfile (Go)

dockerfile
1FROM golang:1.22-alpine AS builder
2WORKDIR /app
3COPY go.mod go.sum ./
4RUN go mod download
5COPY . .
6RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-s -w" -o /server ./cmd/server
7
8FROM alpine:3.19 AS runner
9RUN apk --no-cache add ca-certificates
10RUN adduser -D -u 1001 appuser
11USER appuser
12
13COPY --from=builder /server /server
14
15EXPOSE 8080
16HEALTHCHECK --interval=30s --timeout=3s CMD wget -qO- http://localhost:8080/health || exit 1
17CMD ["/server"]

Multi-Stage Dockerfile (Python/Django)

dockerfile
1FROM python:3.12-slim AS builder
2WORKDIR /app
3RUN pip install --no-cache-dir uv
4COPY requirements.txt .
5RUN uv pip install --system --no-cache -r requirements.txt
6
7FROM python:3.12-slim AS runner
8WORKDIR /app
9
10RUN useradd -r -u 1001 appuser
11USER appuser
12
13COPY --from=builder /usr/local/lib/python3.12/site-packages /usr/local/lib/python3.12/site-packages
14COPY --from=builder /usr/local/bin /usr/local/bin
15COPY . .
16
17ENV PYTHONUNBUFFERED=1
18EXPOSE 8000
19
20HEALTHCHECK --interval=30s --timeout=3s CMD python -c "import urllib.request; urllib.request.urlopen('http://localhost:8000/health/')" || exit 1
21CMD ["gunicorn", "config.wsgi:application", "--bind", "0.0.0.0:8000", "--workers", "4"]

Docker Best Practices

# GOOD practices
- Use specific version tags (node:22-alpine, not node:latest)
- Multi-stage builds to minimize image size
- Run as non-root user
- Copy dependency files first (layer caching)
- Use .dockerignore to exclude node_modules, .git, tests
- Add HEALTHCHECK instruction
- Set resource limits in docker-compose or k8s

# BAD practices
- Running as root
- Using :latest tags
- Copying entire repo in one COPY layer
- Installing dev dependencies in production image
- Storing secrets in image (use env vars or secrets manager)

CI/CD Pipeline

GitHub Actions (Standard Pipeline)

yaml
1name: CI/CD
2
3on:
4  push:
5    branches: [main]
6  pull_request:
7    branches: [main]
8
9jobs:
10  test:
11    runs-on: ubuntu-latest
12    steps:
13      - uses: actions/checkout@v4
14      - uses: actions/setup-node@v4
15        with:
16          node-version: 22
17          cache: npm
18      - run: npm ci
19      - run: npm run lint
20      - run: npm run typecheck
21      - run: npm test -- --coverage
22      - uses: actions/upload-artifact@v4
23        if: always()
24        with:
25          name: coverage
26          path: coverage/
27
28  build:
29    needs: test
30    runs-on: ubuntu-latest
31    if: github.ref == 'refs/heads/main'
32    steps:
33      - uses: actions/checkout@v4
34      - uses: docker/setup-buildx-action@v3
35      - uses: docker/login-action@v3
36        with:
37          registry: ghcr.io
38          username: ${{ github.actor }}
39          password: ${{ secrets.GITHUB_TOKEN }}
40      - uses: docker/build-push-action@v5
41        with:
42          push: true
43          tags: ghcr.io/${{ github.repository }}:${{ github.sha }}
44          cache-from: type=gha
45          cache-to: type=gha,mode=max
46
47  deploy:
48    needs: build
49    runs-on: ubuntu-latest
50    if: github.ref == 'refs/heads/main'
51    environment: production
52    steps:
53      - name: Deploy to production
54        run: |
55          # Platform-specific deployment command
56          # Railway: railway up
57          # Vercel: vercel --prod
58          # K8s: kubectl set image deployment/app app=ghcr.io/${{ github.repository }}:${{ github.sha }}
59          echo "Deploying ${{ github.sha }}"

Pipeline Stages

PR opened:
  lint → typecheck → unit tests → integration tests → preview deploy

Merged to main:
  lint → typecheck → unit tests → integration tests → build image → deploy staging → smoke tests → deploy production

Health Checks

Health Check Endpoint

typescript
1// Simple health check
2app.get("/health", (req, res) => {
3  res.status(200).json({ status: "ok" });
4});
5
6// Detailed health check (for internal monitoring)
7app.get("/health/detailed", async (req, res) => {
8  const checks = {
9    database: await checkDatabase(),
10    redis: await checkRedis(),
11    externalApi: await checkExternalApi(),
12  };
13
14  const allHealthy = Object.values(checks).every(c => c.status === "ok");
15
16  res.status(allHealthy ? 200 : 503).json({
17    status: allHealthy ? "ok" : "degraded",
18    timestamp: new Date().toISOString(),
19    version: process.env.APP_VERSION || "unknown",
20    uptime: process.uptime(),
21    checks,
22  });
23});
24
25async function checkDatabase(): Promise<HealthCheck> {
26  try {
27    await db.query("SELECT 1");
28    return { status: "ok", latency_ms: 2 };
29  } catch (err) {
30    return { status: "error", message: "Database unreachable" };
31  }
32}

Kubernetes Probes

yaml
1livenessProbe:
2  httpGet:
3    path: /health
4    port: 3000
5  initialDelaySeconds: 10
6  periodSeconds: 30
7  failureThreshold: 3
8
9readinessProbe:
10  httpGet:
11    path: /health
12    port: 3000
13  initialDelaySeconds: 5
14  periodSeconds: 10
15  failureThreshold: 2
16
17startupProbe:
18  httpGet:
19    path: /health
20    port: 3000
21  initialDelaySeconds: 0
22  periodSeconds: 5
23  failureThreshold: 30    # 30 * 5s = 150s max startup time

Environment Configuration

Twelve-Factor App Pattern

bash
1# All config via environment variables — never in code
2DATABASE_URL=postgres://user:pass@host:5432/db
3REDIS_URL=redis://host:6379/0
4API_KEY=${API_KEY}           # injected by secrets manager
5LOG_LEVEL=info
6PORT=3000
7
8# Environment-specific behavior
9NODE_ENV=production          # or staging, development
10APP_ENV=production           # explicit app environment

Configuration Validation

typescript
1import { z } from "zod";
2
3const envSchema = z.object({
4  NODE_ENV: z.enum(["development", "staging", "production"]),
5  PORT: z.coerce.number().default(3000),
6  DATABASE_URL: z.string().url(),
7  REDIS_URL: z.string().url(),
8  JWT_SECRET: z.string().min(32),
9  LOG_LEVEL: z.enum(["debug", "info", "warn", "error"]).default("info"),
10});
11
12// Validate at startup — fail fast if config is wrong
13export const env = envSchema.parse(process.env);

Rollback Strategy

Instant Rollback

bash
1# Docker/Kubernetes: point to previous image
2kubectl rollout undo deployment/app
3
4# Vercel: promote previous deployment
5vercel rollback
6
7# Railway: redeploy previous commit
8railway up --commit <previous-sha>
9
10# Database: rollback migration (if reversible)
11npx prisma migrate resolve --rolled-back <migration-name>

Rollback Checklist

• Previous image/artifact is available and tagged
• Database migrations are backward-compatible (no destructive changes)
• Feature flags can disable new features without deploy
• Monitoring alerts configured for error rate spikes
• Rollback tested in staging before production release

Production Readiness Checklist

Before any production deployment:

Application

• All tests pass (unit, integration, E2E)
• No hardcoded secrets in code or config files
• Error handling covers all edge cases
• Logging is structured (JSON) and does not contain PII
• Health check endpoint returns meaningful status

Infrastructure

• Docker image builds reproducibly (pinned versions)
• Environment variables documented and validated at startup
• Resource limits set (CPU, memory)
• Horizontal scaling configured (min/max instances)
• SSL/TLS enabled on all endpoints

Monitoring

• Application metrics exported (request rate, latency, errors)
• Alerts configured for error rate > threshold
• Log aggregation set up (structured logs, searchable)
• Uptime monitoring on health endpoint

Security

• Dependencies scanned for CVEs
• CORS configured for allowed origins only
• Rate limiting enabled on public endpoints
• Authentication and authorization verified
• Security headers set (CSP, HSTS, X-Frame-Options)

Operations

• Rollback plan documented and tested
• Database migration tested against production-sized data
• Runbook for common failure scenarios
• On-call rotation and escalation path defined