The shared 1 req/sec MB rate limiter was serializing the 3 concurrent
search calls in Phase 1 to ~3s minimum. Interactive search needs short
bursts (3 calls at once) but not sustained throughput.
Split into two MB rate limiters:
- mbSearchLimiter: burst=3, refill=1/sec — allows one search's 3
concurrent calls to fire immediately, then rate-limits sustained use
- mbBackgroundLimiter: strict 1/sec — gates artist image resolution
in the indexer to avoid 429s during sustained background work
Added NewRateLimiterBurst(n, b) constructor for configurable burst.
Expected Phase 1 improvement: ~3.5s → ~1s (3 calls fire in parallel
instead of serializing through the limiter).
yonlu
fd29a6c99d