Result cache: size the process-memory LRU with RESULT_CACHE_MB

CLAUDE.md

@@ -162,7 +162,8 @@ changing first. The parts, and the one place each rule lives:
    - **`RESULT_CACHE=off` turns it off.** `throughCache` then runs the direct call on every
      request, so a server answers everything cold — for measuring what a first reader waits for.
      Without a cache handler configured (anywhere but Vercel), the cache is the Node process's own
-     50 MB LRU (`cacheMaxMemorySize`): lost on restart, and not shared between replicas.
+     LRU (`cacheMaxMemorySize`, 50 MB unless `RESULT_CACHE_MB` says otherwise): lost on restart,
+     and not shared between replicas.
    - **Arguments are the key.** A cached function takes only serializable arguments and computes
      everything else itself; a function passed in cannot be called. Anything that changes the
      answer must be an argument.

docs/ENVIRONMENT.md

@@ -131,6 +131,7 @@ see the security notes below.
 | var | default | meaning |
 |---|---|---|
 | `RESULT_CACHE` | on | `off`: answer every request directly, bypassing the result cache, to measure what a first reader waits for |
+| `RESULT_CACHE_MB` | `50` | the result cache's size in MB where it is process memory (anywhere but Vercel); read at server start |
 | `CLICKHOUSE_MAX_INFLIGHT` | `8` | ClickHouse queries in flight at once per process; the rest queue (`docs/PERFORMANCE.md`) |
 | `EXPLORE_COHORT_EXTERNAL_LIMIT` | `50000` | the most patient ids Explore ships to ClickHouse for one draft cohort |
 | `ONCOPRINT_CLUSTER_LIMIT` | `4000` | the most columns an oncoprint clusters (`cluster:<profile>` sort) |

next.config.mjs

@@ -27,6 +27,9 @@ const nextConfig = (phase) => ({
   distDir: process.env.NEXT_DIST_DIR || ".next",
   // `'use cache: remote'` (lib/next-cache.ts) needs Cache Components
   cacheComponents: true,
+  // Off Vercel that cache is this process-memory LRU; `next start` reads it at startup, so a
+  // deployment sizes it without a rebuild
+  cacheMaxMemorySize: (Number(process.env.RESULT_CACHE_MB) || 50) * 1024 * 1024,
   // hosts besides localhost that may load `next dev`'s scripts and HMR socket (e.g. a tailnet
   // proxy in front of a dev server); comma-separated, dev only
   allowedDevOrigins: (process.env.ALLOWED_DEV_ORIGINS || "").split(",").map((h) => h.trim()).filter(Boolean),