perf(nats): Implement bulk cache prewarming for runners to optimize startup performance

src/nats/RunnerKV.ts

@@ -126,3 +126,65 @@ export async function warmRunner(runnerId: number): Promise<RunnerKVEntry> {
     await setRunnerEntry(runnerId, entry);
     return entry;
 }
+
+/**
+ * Bulk cache prewarming: loads all runners from the database and populates the KV cache.
+ * Uses 3 efficient queries and parallel KV writes to minimize startup time.
+ *
+ * Call from loader during startup (if NATS_PREWARM=true) to eliminate DB reads on the hot
+ * path from the very first scan.
+ */
+export async function warmAll(): Promise<void> {
+    const connection = getConnection();
+
+    // Query 1: All runners
+    const runners = await connection
+        .getRepository(Runner)
+        .createQueryBuilder('runner')
+        .select(['runner.id', 'runner.firstname', 'runner.lastname'])
+        .getMany();
+
+    // Query 2: Total valid distance per runner
+    const distanceResults = await connection
+        .getRepository(TrackScan)
+        .createQueryBuilder('scan')
+        .select('scan.runner', 'runnerId')
+        .addSelect('COALESCE(SUM(track.distance), 0)', 'total')
+        .innerJoin('scan.track', 'track')
+        .where('scan.valid = :valid', { valid: true })
+        .groupBy('scan.runner')
+        .getRawMany();
+
+    // Query 3: Latest valid scan timestamp per runner
+    const latestResults = await connection
+        .getRepository(TrackScan)
+        .createQueryBuilder('scan')
+        .select('scan.runner', 'runnerId')
+        .addSelect('MAX(scan.timestamp)', 'latestTimestamp')
+        .where('scan.valid = :valid', { valid: true })
+        .groupBy('scan.runner')
+        .getRawMany();
+
+    // Build lookup maps
+    const distanceMap = new Map<number, number>();
+    distanceResults.forEach((row: any) => {
+        distanceMap.set(parseInt(row.runnerId, 10), parseInt(row.total, 10));
+    });
+
+    const latestMap = new Map<number, number>();
+    latestResults.forEach((row: any) => {
+        latestMap.set(parseInt(row.runnerId, 10), parseInt(row.latestTimestamp, 10));
+    });
+
+    // Write all entries in parallel
+    const writePromises = runners.map((runner) => {
+        const entry: RunnerKVEntry = {
+            displayName: `${runner.firstname} ${runner.lastname}`,
+            totalDistance: distanceMap.get(runner.id) ?? 0,
+            latestTimestamp: latestMap.get(runner.id) ?? 0,
+        };
+        return setRunnerEntry(runner.id, entry);
+    });
+
+    await Promise.all(writePromises);
+}