Why Google Calendar Booking Systems Double-Book
Why Google Calendar booking automations can double-book, and where the workflow needs stronger safeguards.
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#Concurrency
5 posts
An App Where Many Write to One Sheet: Concurrency, Duplicates, and Export Design
The places I actually got stuck building the CheckReport Demo, with the code. Concurrent saves to a shared sheet are blocked with ScriptLock + an idempotency key, cells hold only metadata, and exports are cut off with a time budget. Good code and bad code, side by side.
Concurrent Writes to the Same Sheet Break: LockService and the 30-Run Ceiling
When users and triggers write the same asset, numbers collide and rows get overwritten. Guard with tryLock + finally + flush, and design for the 30-per-user concurrency ceiling.
Your /exec URL Must Not Change on Every Redeploy
Reuse the deployment ID when you push a new version with clasp and the /exec URL stays fixed. Guard shared sheet writes with LockService.
External Calls Fail Sometimes: Exponential Backoff and a Retry Budget
Transient failures like 429, 503, and timeouts can be recovered by retrying. But never retry a non-idempotent write without an idempotency key, and stop before 6 minutes.