---
phase: 32-state-update-optimization
plan: 01
subsystem: performance
tags: [react, redux, debounce, performance, hooks]

# Dependency graph
requires:
  - phase: 31-selector-optimization
    provides: Optimized Redux selectors with composition and memoization
provides:
  - useDebounceCallback hook with ref-based pattern for stable debounced callbacks
  - Single debounced track sync call replacing triple setTimeout pattern
  - Stable trackChanges debounce that doesn't reset on dependency changes
affects: [33-performance-testing, state-management, session-sync]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "Ref-based debounce pattern for React hooks"
    - "useMemo + debounce for stable function instances"
    - "useDebounceCallback hook for reusable debounced callbacks"

key-files:
  created:
    - jam-ui/src/hooks/useDebounceCallback.js
  modified:
    - jam-ui/src/components/client/JKSessionScreen.js
    - jam-ui/src/hooks/useSessionModel.js

key-decisions:
  - "1.5s debounce delay for track sync (covers mixer initialization window)"
  - "useDebounceCallback with ref pattern prevents stale closures"
  - "useMemo with empty deps creates stable debounced function"

patterns-established:
  - "useDebounceCallback pattern: useRef stores callback, useMemo creates debounce once, always reads fresh values"
  - "Single debounced API call pattern: useMemo + debounce + cleanup on unmount"

# Metrics
duration: 3min
completed: 2026-03-05
---

# Phase 32 Plan 01: Redundant Operations Fix Summary

**Single debounced track sync and stable debounce timers eliminate redundant API calls and timer resets**

## Performance

- **Duration:** 3 min
- **Started:** 2026-03-05T00:00:00Z
- **Completed:** 2026-03-05T00:03:04Z
- **Tasks:** 3
- **Files modified:** 3 (1 created, 2 modified)

## Accomplishments
- Created useDebounceCallback hook solving stale closure problem with debounced callbacks
- Replaced triple setTimeout pattern (1s, 1.4s, 6s) with single 1.5s debounced call
- Fixed trackChanges debounce timer resetting on dependency changes

## Task Commits

Each task was committed atomically:

1. **Task 1: Create useDebounceCallback hook** - `1a42be980` (feat)
2. **Task 2: Consolidate track sync to single debounced call** - `de5b331e0` (feat)
3. **Task 3: Fix trackChanges debounce in useSessionModel** - `f0ddd9d7c` (feat)

## Files Created/Modified
- `jam-ui/src/hooks/useDebounceCallback.js` - Reusable ref-based debounce hook that solves stale closure problem
- `jam-ui/src/components/client/JKSessionScreen.js` - Replaced triple track sync timers with single debounced call
- `jam-ui/src/hooks/useSessionModel.js` - Updated trackChanges to use useDebounceCallback for stable timer

## Decisions Made

1. **1.5s debounce delay for track sync**
   - Legacy used 1s, 1.4s, and 6s delays
   - First two calls (1s, 1.4s) were redundant
   - Single 1.5s delay covers mixer initialization window
   - Can increase if slow network issues arise

2. **useDebounceCallback pattern with refs**
   - useRef stores latest callback (always current)
   - useMemo creates debounce once with [delay] deps only
   - Callback reads fresh closure values via ref
   - Timer stable across state changes

3. **Remove lodash debounce import from useSessionModel**
   - trackChanges was only usage in file
   - useDebounceCallback handles debouncing internally
   - Cleaner dependency graph

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

None - implementation proceeded smoothly with ESLint auto-fix handling pre-existing formatting issues.

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness

**Ready for performance testing:**
- Track sync now fires once per session join (not 3 times)
- Debounce timers stable across state changes
- All changes backward-compatible with existing session join flow
- Ready for performance measurement and validation

**Blockers/concerns:**
- None

**Testing recommendations for next phase:**
- Verify track sync fires exactly once after session join
- Measure API call count reduction (expect 66% reduction from 3 to 1)
- Verify trackChanges debounce timer doesn't reset during rapid state updates
- Test session join on slow networks (may need to increase 1.5s delay)

---
*Phase: 32-state-update-optimization*
*Completed: 2026-03-05*
