Fix /api/markets/movers timeout and make /api/health honest

[VittorioC13]

Summary

Production /api/markets/movers has been timing out 100% of the time for 8 days (since 5/4 16:00 UTC). The marketing bot built on top of the API has been silently broken — /api/health returned "status": "healthy" the whole time because it only probed 10 markets per source and never checked KV reachability or movers freshness.

Root cause: the movers handler did 1,600 sequential kv.get() calls inside detectMovers() (one per tracked market), plus 1,600 KV writes via recordPriceSnapshots(), all in the request path. Once @vercel/kv's Upstash migration added a small amount of per-request latency, total runtime crossed the 25s function timeout and never recovered.

Changes

• api/lib/price-snapshots.ts (new): detectMoversBatch() uses kv.mget() in chunks of 100, replacing 1,600 individual reads with ~16 batched calls. recordPriceSnapshots() now reads via mget and caps each market's snapshot array at 300 entries.
• api/cron/refresh-markets.ts (new): runs every 2 minutes, refreshes markets, records snapshots, precomputes movers for buckets 0.02/0.05/0.1/0.2 into movers:precomputed:<bucket> with a 5-minute TTL. Writes freshness timestamps for /api/health to consume.
• api/markets/movers.ts (rewrite): now read-only — single kv.get() of the precomputed bucket, in-memory filter for limit/category, 20s in-process response cache. Returns 503 if the cron hasn't run since deploy.
• api/health.ts (rewrite): 4 honest sub-checks — real market counts (Poly ≥ 800, Kalshi ≥ 200), KV read+write probe, snapshot freshness (< 5min), movers freshness (< 5min). Returns 503 on any degraded check so external monitors actually fire.
• vercel.json: added refresh-markets cron entry and rewrite.

Test plan

• pnpm typecheck (already green locally)
• Deploy to a preview env and confirm /api/cron/refresh-markets (with Authorization: Bearer $CRON_SECRET) completes in <10s and writes both meta:last_snapshot_run and movers:precomputed:0.05 keys
• time curl https://<preview>/api/markets/movers returns in <1s with count > 0
• curl https://<preview>/api/health | jq shows polymarket.markets >= 1200, kalshi.markets >= 400, and status: "healthy"
• After preview burns in, promote to production and re-run the marketing bot end-to-end

Rollback

Phase 1 (mget batching) has no schema change. If anything goes wrong after deploy, git revert restores the prior endpoint; precomputed KV keys naturally expire in 5 minutes. The price_history:* data shape is unchanged.

🤖 Generated with Claude Code

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
musashi	Ready	Preview, Comment	May 12, 2026 1:54pm