Blocking call on hot path

Performance

Last updated: October 21, 2025

Overview

Bug Type:
Blocking call on hot path
Category:
Performance

Definition

Synchronous or slow work on a high-traffic path inflates latency and harms throughput.

How to fix Blocking call on hot path?

Move work off main thread; batch/chunk tasks; precompute/cache; use workers/queues; profile and set SLIs for latency

Symptoms

Observable signs that may indicate Blocking call on hot path:

  • Latency spikes and long tasks on main thread/event loop.
  • Throughput drops under CPU-bound sections.
  • User-visible jank during heavy computation.

Example Errors:

  • Long Task detected (>50ms)
  • Event loop blocked warnings
  • High CPU usage on single thread

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