The fluctuation in metric values (e.g., 80 → 84 → 80) when you refresh data on your Mixpanel board can be explained by a combination of Mixpanel's query result caching and its deduplication mechanisms.
1. Query Result Caching:
Mixpanel caches report results for performance reasons. The cache duration depends on the date range of your query (from 1 hour up to 14 days). When you refresh the data, Mixpanel may fetch the latest data from the backend, which could include newly ingested events or reflect changes due to deduplication or late-arriving data. This can cause the numbers to fluctuate as the cache is invalidated and the most up-to-date data is shown Query Result Caching.
2. Deduplication Algorithm:
Mixpanel uses two deduplication processes:
- Query-Time Deduplication: Happens immediately in the UI. If duplicate events (same event name, distinct_id, timestamp, and $insert_id) exist, only the most recent is shown in reports.
- Compaction-Time Deduplication: Runs periodically in the backend (after a few hours and again after about 20 days). It removes older duplicates based on event name, distinct_id, and $insert_id (timestamp only needs to match the same day). This process can retroactively change event counts as duplicates are removed from storage Deduplication Mechanisms.
Why do values fluctuate?
- When you refresh, you may see different values if deduplication has recently processed and removed duplicates, or if late-arriving data has been ingested.
- The initial value (e.g., 80) could reflect the state before deduplication or late data ingestion. After a refresh, the value might increase (e.g., 84) if new events arrived, or decrease back (e.g., 80) if deduplication removed duplicates that were previously counted.
- This is expected behavior as Mixpanel's backend processes catch up and ensure your reports reflect the most accurate, deduplicated data.
Summary:
Fluctuating values on refresh are most commonly due to a combination of cache invalidation (showing the latest data) and the deduplication process (removing or consolidating duplicate events), both of which can change the underlying event counts in your reports Query Result Caching, Deduplication Mechanisms.
