Separate transport duplicates from repeat taps
A resent event may share the same external identifier and timestamp. A second physical tap can have a new timestamp a few seconds later. Keep these cases distinct: integration-level deduplication and attendance interpretation solve different problems, even when both reduce repeated rows.
Choose a narrow review rule
Consider employee ID, device, direction and elapsed time together. A broad time window may discard a legitimate exit and re-entry. Test any rule against real operational patterns, especially locations with adjacent readers or frequent short movements. Keep questionable records visible for review.
Measure whether the fix works
Track duplicate volume by reader and import batch. A sudden rise after an integration update suggests a different cause from one slow physical reader. Compare calculated hours before and after a rule change using a sample of approved days.
Worked example
Two IN events five seconds apart may be a repeated tap. An OUT followed by an IN several minutes later may represent a real movement. Direction and context matter more than proximity alone.
Practical checklist
- Retain original event identifiers.
- Test repeat taps separately from resent imports.
- Review the effect on approved daily hours.