What causes duplicate analytics events created on retry?

The server received and stored a batch but its response was lost, so the client retries and the backend ingests the same events twice.

How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix Duplicate Analytics Events Created on Retry

Quick answer: Generate a stable unique event_id (UUID) on the client at creation time and have the backend reject or merge any event_id it has already seen.

A dropped 200 response makes the client resend a batch that already landed, so purchases and conversions count twice and inflate revenue. A client-side dedup key fixes this at the source.

How to fix it

1. Generate a stable event_id

Assign each event a UUID when it is created, not when it is sent. The id must survive serialization to disk so a retry carries the same value as the original attempt.

2. Deduplicate on the server

Have ingestion key on event_id and ignore inserts for ids already present (e.g. INSERT ... ON DUPLICATE KEY IGNORE). Retries then become safe no-ops.

3. Keep a recent-id window

If full storage is impractical, dedup against the last N minutes of ids, which covers realistic retry windows. This bounds the dedup index while still catching resend storms.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.

Reproduce it once with full context and the fix writes itself. The hunt is the expensive part.