Code Deployment Pipeline

Developer pushes code. CI builds and tests inside isolated ephemeral containers. An immutable, SHA-tagged artifact is stored in an S3-backed content-addressed store. CD does a canary deploy to 1% of traffic, runs automated statistical analysis comparing canary vs baseline metrics over 15 minutes, then progressively promotes: 10% → 50% → 100%. Rollback = re-deploy the previous artifact — no new build needed. Feature flags decouple deploy from release: ship code dark, enable for 1% → 100% independently. Google, Netflix, Meta — same pattern, different scale.

Time budget: 45 min whiteboard. Draw architecture, estimate numbers, discuss tradeoffs.

Hint 1

Lead with immutability. "Artifacts are SHA-tagged and never overwritten. Rollback is just re-pointing to the previous SHA." This single idea simplifies everything.

Hint 2

Name the statistical test. "Mann-Whitney U for canary analysis" — shows you've thought beyond "just check if errors go up."

Hint 3

Distinguish deploy from release. "Deploy puts code on servers. Release exposes it to users. Feature flags let you do these independently." This nuance impresses.

• +2 Lead with immutability. "Artifacts are SHA-tagged and never overwritten. Rollback is just re-pointing to the previous SHA." This single idea simplifies everything.
• +2 Name the statistical test. "Mann-Whitney U for canary analysis" — shows you've thought beyond "just check if errors go up."
• +2 Distinguish deploy from release. "Deploy puts code on servers. Release exposes it to users. Feature flags let you do these independently." This nuance impresses.
• +2 Talk about blast radius. "Canary at 1% means worst case, 1% of users see a regression for 15 minutes before auto-rollback." Quantify the risk.
• +2 Mention hermetic builds. "No network during build. Dependencies from a pre-populated cache. Same commit = same artifact, always." Production-grade insight.

Self-score: tally the points you would have mentioned unprompted. 7+ is interview-ready on this problem.

• Deploy on Friday at 5 PM — "it's just a small change"
• Mutable artifacts — "just SSH in and patch the JAR on the production server"
• All-at-once deploy with no canary — "we tested it in staging, ship it"