Next.js: Edge runtime — типичные gotcha на собеседовании

«Edge faster» — junior; matcher scope, no Node Buffer, env inlined at build, DB connection storms, per-segment runtime — senior answers.

Разбор

• «Edge is faster» junior. Isolate CPU often slower than Node server. Win = cold-start + geo proximity, не throughput.
• Middleware every matched request, before cache. Broad matcher → auth на every static asset. Scope config.matcher.
• No Node Buffer, process.cwd(), dynamic require. Libraries feature-detect Node → wrong branch silently.
• Env vars inlined at build for Edge — runtime-only secrets model differs; check platform.
• Database: raw Postgres under load → thousands isolates → connection exhaustion. HTTP drivers exist for this.
• runtime = 'edge' per-segment. Page и API route могут differ; layout runtime не force children.

Итог

Edge interview = latency not CPU + isolate constraints + never raw DB pool on Edge.