feat(base): env var for duckdb reader-pool size

apps/server/src/core/base/query-cache/query-cache.config.ts

@@ -10,6 +10,7 @@ export type QueryCacheConfig = {
   threads: number;
   trace: boolean;
   tempDirectory: string;
+  readerPoolSize: number;
 };
 
 @Injectable()
@@ -25,6 +26,7 @@ export class QueryCacheConfigProvider {
       threads: env.getBaseQueryCacheThreads(),
       trace: env.getBaseQueryCacheTrace(),
       tempDirectory: env.getBaseQueryCacheTempDirectory(),
+      readerPoolSize: env.getBaseQueryCacheReaderPoolSize(),
     };
   }
 }

apps/server/src/integrations/environment/environment.service.ts

@@ -385,4 +385,20 @@ export class EnvironmentService {
       10,
     );
   }
+
+  getBaseQueryCacheReaderPoolSize(): number {
+    // Number of reader connections held open against the shared DuckDB
+    // instance. Reads are dispatched via `withReader()` which checks out a
+    // connection, runs the query, returns it. Bigger pool = more concurrent
+    // reads without serialization, at the cost of per-connection overhead
+    // (each connection carries its own catalog snapshot + prepared-statement
+    // cache ~= 300 KB).
+    //
+    // Default 4 matches libuv's default thread-pool size. Raise to 8+ if
+    // you see p99 list latency correlate with concurrent request volume.
+    return parseInt(
+      this.configService.get<string>('BASE_QUERY_CACHE_READER_POOL_SIZE', '4'),
+      10,
+    );
+  }
 }