improvement(scheduler): raise per-tick claim budget to drain backlog

[TheodoreSpeaks]

Summary

• MAX_CRON_CLAIMS 20 → 200; reserved workflow/job slots 10/10 → 100/100.
• The scheduler picker was capped at 20 due items per tick. Once steady-state demand crossed ~20 schedules/min the picker fell behind and never caught up — we saw 18+ hours of sustained Processing 20 due items ticks with a chronic backlog. A workflow scheduled for midnight today only fired at 11:32 UTC because that's when its row finally reached the head of the queue.
• Per-item processing is ~500ms, so 100 items still fits comfortably inside one 60s cron tick (~50s).

Type of Change

• Bug fix

Testing

• bun run lint — clean
• bun run check:api-validation:strict — passes
• No behavior change other than the constant bump; existing claim/lock semantics unchanged.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Skipped		May 12, 2026 7:57pm

[cursor]

PR Summary

Medium Risk
Low code risk (constant-only change), but raising the per-tick claim limits can increase DB locking/queue pressure and runtime per cron tick under heavy backlog.

Overview
Increases the scheduler execution endpoint’s per-cron claim budget by 10×, raising MAX_CRON_CLAIMS to 200 and expanding the reserved workflow/job claim split (workflow reservation to 100, with the remainder for jobs).

This allows each cron tick of apps/sim/app/api/schedules/execute/route.ts to dequeue and queue significantly more due work to help drain sustained scheduling backlogs, without changing the underlying claim/lock logic.

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[greptile-apps]

Greptile Summary

This PR addresses a chronic scheduler backlog by raising MAX_CRON_CLAIMS from 20 to 100 and RESERVED_WORKFLOW_CLAIMS/RESERVED_JOB_CLAIMS from 10 to 50 each, so the picker can drain more than ~20 due items per tick.

• MAX_CRON_CLAIMS 20 → 100; both reserved-slot constants scale proportionally (10 → 50 each), preserving the 50/50 split.
• The overflow reallocation logic (lines 162–166), lock/claim semantics, and DB transaction patterns are all unchanged — only the ceiling values differ.
• Workflow schedules fan out to the async job queue (fast path), but Mothership jobs are always executed inline; that pool now reaches 50 concurrent in-process executions per tick instead of 10.

Confidence Score: 4/5

Safe to merge for the workflow-schedule path; the inline-job path deserves a quick operational check at the new concurrency level before relying on it under full load.

The change touches two integer constants and leaves every lock, claim, transaction, and overflow-reallocation path intact. The only non-trivial risk is the 5x increase in concurrent inline job executions per tick — if those jobs are DB- or network-heavy, a busy tick could see noticeably more resource pressure than before, and there is no observability or back-pressure in place to catch a latency cliff.

apps/sim/app/api/schedules/execute/route.ts — specifically the inline job execution block (lines 316–338) and the executeJobInline implementation it calls.

Important Files Changed

Filename	Overview
apps/sim/app/api/schedules/execute/route.ts	Raises MAX_CRON_CLAIMS 20→100 and RESERVED_WORKFLOW_CLAIMS 10→50 (RESERVED_JOB_CLAIMS derived at 50); overflow budget reallocation logic and claim/lock semantics are unchanged; inline job concurrency scales 5× with no back-pressure guard.

Sequence Diagram

sequenceDiagram
participant Cron as Cron Trigger (60s tick)
participant Handler as /api/schedules/execute
participant DB as Database (FOR UPDATE SKIP LOCKED)
participant Queue as Async Job Queue
participant Inline as executeJobInline
Cron->>Handler: GET (authenticated)
Handler->>DB: "claimWorkflowSchedules(limit=50)"
DB-->>Handler: up to 50 workflow rows (locked)
Handler->>DB: "claimJobSchedules(limit=50)"
DB-->>Handler: up to 50 job rows (locked)
Note over Handler: remainingClaimBudget = 100 - claimed
par Workflow schedules up to 50
Handler->>Queue: enqueue schedule-execution payload
Queue-->>Handler: jobId
and Mothership jobs up to 50 always inline
Handler->>Inline: executeJobInline(payload) x up to 50 concurrent
Inline-->>Handler: done
end
Handler-->>Cron: executedCount N

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Comments Outside Diff (1)

1. apps/sim/app/api/schedules/execute/route.ts, line 316-338 (link)

   Inline job concurrency increase: 10 → 50

   Mothership jobs skip the queue and always execute inline via executeJobInline. With RESERVED_JOB_CLAIMS raised from 10 to 50, up to 50 of these can now fire concurrently inside a single tick via Promise.allSettled. If executeJobInline opens DB connections, issues HTTP calls, or holds locks, that 5× jump in concurrent in-process job work could create resource pressure — especially since the handler has a maxDuration of 3600s and there is no back-pressure mechanism here. Worth adding observability (e.g. timing the allSettled block) to catch any latency cliff before the next scale-up.

_{Reviews (1): Last reviewed commit: "improvement(scheduler): raise per-tick c..." | Re-trigger Greptile}

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