Incrementally Rebuilding Stack Overflow's Monolith
summary
Stack Overflow incrementally rewrites the comments UI inside a modular monolith, rebuilding the frontend in Svelte while keeping .NET Razor server rendering. A Node.js renderer is invoked from .NET (Jering) to SSR components in parallel, which surprisingly improves page performance. Experimentation uses deterministic feature‑flag hashing and multi‑variant AB tests (nine variants); results show putting the avatar above comments lifts upvotes ~20%, larger font reduces comment count but increases upvote score, and an opt‑out rule skews AB splits.
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chapters (18)
- 0:00Rebuilding Stack Overflow's monolith
- 1:15Modular monolith goals
- 3:22Incremental engineering with agile
- 5:06Four ways to gather feedback
- 10:17Feature flagging for A/B testing
- 16:16Rebuilding comments UI
- 21:36Testing user intent with dropdown
- 25:28Challenges with opt-out switches
- 28:56New comments UI design
- 31:02Server vs client UI trade-offs
- 33:10Indiana Jones feature flag experiment
- 35:42Performance with parallel rendering
- 38:08Meta community feedback
- 39:32Metrics after UI change
- 41:01Smaller controlled experiments
- 42:47Four-way A/B test variables
- 45:58Nine-way A/B test results
- 52:04Font size and engagement impact
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