[HIGH] Refactor getNextPaydays to mathematical computation - eliminate day-by-day loop #37

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opened 2026-06-09 00:03:13 +00:00 by Mark · 0 comments

Mark commented

2026-06-09 00:03:13 +00:00

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Location: backend/src/services/PaydayService.ts:24-42

Problem: getNextPaydays uses a brute-force while loop iterating every calendar day until count paydays are found. For biweekly/monthly schedules, this iterates 30–350+ days per call.

Impact: O(days) per lookup. For monthly schedules near month boundaries, this is 10–1,000x slower than necessary.

Fix: Replace with arithmetic:

Weekly: start + ceil((today - start) / 7) * 7
Biweekly: start + ceil((today - start) / 14) * 14
Monthly: new Date(today.getFullYear(), today.getMonth(), dayOfMonth)
Twice-monthly: pick next of [d1, d2] >= today

Effort: ~2 hours

**Location:** `backend/src/services/PaydayService.ts:24-42` **Problem:** `getNextPaydays` uses a brute-force `while` loop iterating every calendar day until `count` paydays are found. For biweekly/monthly schedules, this iterates 30–350+ days per call. **Impact:** O(days) per lookup. For monthly schedules near month boundaries, this is 10–1,000x slower than necessary. **Fix:** Replace with arithmetic: - Weekly: `start + ceil((today - start) / 7) * 7` - Biweekly: `start + ceil((today - start) / 14) * 14` - Monthly: `new Date(today.getFullYear(), today.getMonth(), dayOfMonth)` - Twice-monthly: pick next of `[d1, d2] >= today` **Effort:** ~2 hours