fix(webhooks): create delivery partitions from today forward

Webhook delivery partitions are now created from the current day
forward. Previously, setup also created empty partitions for every past
day in the retention window.

Mono-RevId: d43a9430d57497bffd6cfa8f643cd60ad8b7e5e0

Author: ericallam

internal-packages/webhook-engine/src/engine/partitions.test.ts

@@ -62,13 +62,13 @@ postgresTest("ensurePartitions creates the window and is idempotent", async ({ p
   const now = new Date(Date.UTC(2026, 6, 15));
 
   const first = await ensurePartitions(prisma, { now, lookaheadDays: 7, retentionDays: 3 });
-  // retention(3) back .. lookahead(7) forward, inclusive of both ends = 11 day buckets.
-  expect(first.created).toHaveLength(11);
-  expect(await partitionExists(prisma, partitionName(floorDayUTC(now)))).toBe(true);
+  expect(first.created).toHaveLength(8);
+  expect(first.created[0]).toBe(partitionName(floorDayUTC(now)));
+  expect(await partitionExists(prisma, partitionName(addDays(floorDayUTC(now), -1)))).toBe(false);
 
   const second = await ensurePartitions(prisma, { now, lookaheadDays: 7, retentionDays: 3 });
   expect(second.created).toHaveLength(0);
-  expect(second.existing).toHaveLength(11);
+  expect(second.existing).toHaveLength(8);
 });
 
 postgresTest("createPartition is created-then-exists", async ({ prisma }) => {
@@ -93,13 +93,13 @@ postgresTest(
     ]);
 
     for (const result of results) {
-      expect(result.created.length + result.existing.length).toBe(11);
+      expect(result.created.length + result.existing.length).toBe(8);
     }
     const claimed = results.flatMap((r) => r.created);
-    expect(claimed).toHaveLength(11);
-    expect(new Set(claimed).size).toBe(11);
+    expect(claimed).toHaveLength(8);
+    expect(new Set(claimed).size).toBe(8);
     expect(await partitionExists(prisma, partitionName(floorDayUTC(now)))).toBe(true);
-    expect(await listDatedPartitions(prisma)).toHaveLength(11);
+    expect(await listDatedPartitions(prisma)).toHaveLength(8);
   }
 );
 
@@ -162,7 +162,8 @@ postgresTest(
       const opts = { now, lookaheadDays: 10, retentionDays: 3 };
 
       const first = await bootstrapPartitions(webhookDb, opts);
-      expect(first.created).toHaveLength(14);
+      expect(first.created).toHaveLength(11);
+      expect(first.created[0]).toBe(partitionName(now));
       expect(await partitionExists(webhookDb, old.name)).toBe(true);
       expect(await listDatedPartitions(prisma)).toEqual([]);
 
@@ -303,11 +304,7 @@ containerTestWithIsolatedRedisNoClickhouse(
           { timeout: 15_000 }
         )
         .toEqual({
-          partitions: [
-            partitionName(addDays(now, -1)),
-            partitionName(now),
-            partitionName(addDays(now, 1)),
-          ],
+          partitions: [partitionName(now), partitionName(addDays(now, 1))],
           oldExists: false,
         });
       expect(await app.webhookDelivery.findFirst({ where: { id: delivery.id } })).toMatchObject({

internal-packages/webhook-engine/src/engine/partitions.ts

@@ -192,14 +192,17 @@ export type EnsureResult = {
   deferred: string[]; // children we couldn't detach/drop this run; retried next run
 };
 
-/** Create the initial window without running retention. Safe to repeat before enabling ingress. */
+/**
+ * Create today's partition and the lookahead without running retention. Safe to repeat before
+ * enabling ingress. Never creates past days: ingest stamps `createdAt` at insert time, so it never
+ * writes to one. Anything that backfills older rows (the dev delivery seed) creates its own.
+ */
 export async function bootstrapPartitions(
   prisma: WebhookDatabase,
   opts: EnsureOptions
 ): Promise<Pick<EnsureResult, "created" | "existing">> {
-  const today = floorDayUTC(opts.now);
-  const start = addDays(today, -opts.retentionDays);
-  const end = addDays(today, opts.lookaheadDays);
+  const start = floorDayUTC(opts.now);
+  const end = addDays(start, opts.lookaheadDays);
 
   const result: Pick<EnsureResult, "created" | "existing"> = { created: [], existing: [] };