Problem Statement

The mutation execution pipeline executes on every state transition. Three redundant per call allocations dominated latency:

• GetSnapshot(): lock(_lock) + _interceptors.ToArray() - copies entire list even when unchanged
• GetApplicable(): always allocates List<T> + .ToArray(), even if all interceptors pass filter
• Array allocation: each call allocates new arrays regardless of filtering requirements

Solution Overview

1. Volatile Snapshot Cache with Lazy Rebuild

private volatile IMutationInterceptor[]? _snapshotCache = Array.Empty<IMutationInterceptor>();

• volatile ensures readers observe fully published arrays without torn references
• Lazy rebuild on first read after registration changes
• Zero lock acquisition on hot path reads are lock free

2. ArrayPool Based Filtering

var buffer = ArrayPool<IMutationInterceptor>.Shared.Rent(snapshot.Length);

• Eliminates List<T> allocation entirely
• Reuses pooled buffers for filtered results
• Returns snapshot directly when no interceptors are filtered

3. ExecutionId Optimization

• Replaced Guid.NewGuid().ToString() with Interlocked.Increment hex counter
• Result: 8 character hex string instead of 36 character GUID

Performance Impact

Key Design Decisions

Files Changed

InterceptorPipeline.cs

• Added volatile IMutationInterceptor[]? _snapshotCache
• Implemented lazy rebuild in GetSnapshot() with double checked locking
• Replaced List<T> with ArrayPool<T> in GetApplicable()
• Added [MethodImpl(MethodImplOptions.AggressiveInlining)] for hot path methods
• Updated XML documentation

MutationEngine.cs

• Replaced Guid.NewGuid().ToString() with Interlocked.Increment(ref _executionCounter).ToString("x8")
• Added private static long _executionCounter

Migration