From ac8e686f33aa5bdf86f722310ebba148bdc85892 Mon Sep 17 00:00:00 2001
From: Frank <frank@anoma.ly>
Date: Sat, 30 May 2026 10:53:23 -0400
Subject: [PATCH] zen: batch balance calculation

---
 .../app/src/routes/zen/util/handler.ts        | 34 ++++++++++++++-----
 .../app/src/routes/zen/util/usageBatcher.ts   | 31 +++++++++++++++++
 2 files changed, 57 insertions(+), 8 deletions(-)
 create mode 100644 packages/console/app/src/routes/zen/util/usageBatcher.ts

diff --git a/packages/console/app/src/routes/zen/util/handler.ts b/packages/console/app/src/routes/zen/util/handler.ts
index ed76c16c1a..4438688c22 100644
--- a/packages/console/app/src/routes/zen/util/handler.ts
+++ b/packages/console/app/src/routes/zen/util/handler.ts
@@ -47,6 +47,7 @@ import { i18n, type Key } from "~/i18n"
 import { localeFromRequest } from "~/lib/language"
 import { createModelTpmLimiter } from "./modelTpmLimiter"
 import { createModelTpsLimiter } from "./modelTpsLimiter"
+import { accumulateUsage, HOT_WORKSPACES } from "./usageBatcher"
 
 type ZenData = Awaited<ReturnType<typeof ZenData.list>>
 type RetryOptions = {
@@ -981,6 +982,19 @@ export async function handler(
     authInfo = authInfo!
 
     const cost = centsToMicroCents(totalCostInCent)
+
+    // For hot workspaces, batch balance/usage updates through Redis to avoid
+    // row-level lock contention on BillingTable/UserTable. Returns the amount
+    // to flush this request, or null to skip the DB writes entirely.
+    const balanceFlush = await (async () => {
+      if (billingSource !== "subscription" && billingSource !== "lite" && HOT_WORKSPACES.has(authInfo.workspaceID)) {
+        const workspaceCost = billingSource === "free" || billingSource === "byok" ? 0 : cost
+        const flush = await accumulateUsage(authInfo.workspaceID, authInfo.user.id, workspaceCost, cost)
+        return { batched: true as const, flush }
+      }
+      return { batched: false as const, flush: null }
+    })()
+
     await Database.use((db) =>
       Promise.all([
         db.insert(UsageTable).values({
@@ -1082,18 +1096,22 @@ export async function handler(
             ]
           }
 
+          // Batched hot workspace: skip DB writes unless this request is the flush.
+          if (balanceFlush.batched && !balanceFlush.flush) return []
+
+          const workspaceDelta = balanceFlush.flush?.workspaceCost ?? cost
+          const userDelta = balanceFlush.flush?.userCost ?? cost
+          const balanceDelta = billingSource === "free" || billingSource === "byok" ? 0 : workspaceDelta
+
           return [
             db
               .update(BillingTable)
               .set({
-                balance:
-                  billingSource === "free" || billingSource === "byok"
-                    ? sql`${BillingTable.balance} - ${0}`
-                    : sql`${BillingTable.balance} - ${cost}`,
+                balance: sql`${BillingTable.balance} - ${balanceDelta}`,
                 monthlyUsage: sql`
               CASE
-                WHEN MONTH(${BillingTable.timeMonthlyUsageUpdated}) = MONTH(now()) AND YEAR(${BillingTable.timeMonthlyUsageUpdated}) = YEAR(now()) THEN ${BillingTable.monthlyUsage} + ${cost}
-                ELSE ${cost}
+                WHEN MONTH(${BillingTable.timeMonthlyUsageUpdated}) = MONTH(now()) AND YEAR(${BillingTable.timeMonthlyUsageUpdated}) = YEAR(now()) THEN ${BillingTable.monthlyUsage} + ${workspaceDelta}
+                ELSE ${workspaceDelta}
               END
             `,
                 timeMonthlyUsageUpdated: sql`now()`,
@@ -1104,8 +1122,8 @@ export async function handler(
               .set({
                 monthlyUsage: sql`
               CASE
-                WHEN MONTH(${UserTable.timeMonthlyUsageUpdated}) = MONTH(now()) AND YEAR(${UserTable.timeMonthlyUsageUpdated}) = YEAR(now()) THEN ${UserTable.monthlyUsage} + ${cost}
-                ELSE ${cost}
+                WHEN MONTH(${UserTable.timeMonthlyUsageUpdated}) = MONTH(now()) AND YEAR(${UserTable.timeMonthlyUsageUpdated}) = YEAR(now()) THEN ${UserTable.monthlyUsage} + ${userDelta}
+                ELSE ${userDelta}
               END
             `,
                 timeMonthlyUsageUpdated: sql`now()`,
diff --git a/packages/console/app/src/routes/zen/util/usageBatcher.ts b/packages/console/app/src/routes/zen/util/usageBatcher.ts
new file mode 100644
index 0000000000..315ce0a2eb
--- /dev/null
+++ b/packages/console/app/src/routes/zen/util/usageBatcher.ts
@@ -0,0 +1,31 @@
+import { Resource } from "@opencode-ai/console-resource"
+import { getRedis } from "./redis"
+
+// Workspaces whose balance/usage updates should be batched in Redis to avoid
+// row-level lock contention on BillingTable / UserTable.
+export const HOT_WORKSPACES = new Set<string>([
+  "wrk_01KJ8PX5CH50Y4YNGNS9ZR8YDC", // invoice
+])
+
+// Probability that a given request flushes the accumulated totals to the DB.
+// Lower = fewer DB writes, more staleness. ~1 in 100 -> ~1% of requests write.
+const FLUSH_PROBABILITY = 1 / 100
+
+export async function accumulateUsage(workspaceID: string, userID: string, workspaceCost: number, userCost: number) {
+  const redis = getRedis()
+  const wKey = `${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 }
+}