zen: batch balance calculation

packages/console/app/src/routes/zen/util/usageBatcher.ts

@@ -0,0 +1,31 @@
+import { Resource } from "@opencode-ai/console-resource"
+import { getRedis } from "./redis"
+
+// Workspaces whose balance/usage updates should be batched in Redis to avoid
+// row-level lock contention on BillingTable / UserTable.
+export const HOT_WORKSPACES = new Set<string>([
+  "wrk_01KJ8PX5CH50Y4YNGNS9ZR8YDC", // invoice
+])
+
+// Probability that a given request flushes the accumulated totals to the DB.
+// Lower = fewer DB writes, more staleness. ~1 in 100 -> ~1% of requests write.
+const FLUSH_PROBABILITY = 1 / 100
+
+export async function accumulateUsage(workspaceID: string, userID: string, workspaceCost: number, userCost: number) {
+  const redis = getRedis()
+  const wKey = `${Resource.App.stage}:usage:wrk:${workspaceID}`
+  const uKey = `${Resource.App.stage}:usage:usr:${workspaceID}:${userID}`
+
+  await Promise.all([redis.incrby(wKey, workspaceCost), redis.incrby(uKey, userCost)])
+
+  if (Math.random() > FLUSH_PROBABILITY) return null
+
+  // Atomically take the current totals and reset to 0
+  const [workspaceTotal, userTotal] = await Promise.all([redis.getdel<number>(wKey), redis.getdel<number>(uKey)])
+
+  const workspaceFlush = Number(workspaceTotal ?? 0)
+  const userFlush = Number(userTotal ?? 0)
+  if (workspaceFlush === 0 && userFlush === 0) return null
+
+  return { workspaceCost: workspaceFlush, userCost: userFlush }
+}