CPU high because network blocking
When network calls block, threads pile up and the system looks CPU-hot even though compute demand is low.
Common symptoms
- CPU rises with network-dependent workloads
- Latency spikes align with downstream slowness
- Workers pile up without useful progress
Likely causes
- Slow downstream services
- Missing timeouts
- Synchronous network calls in hot paths
Evidence to look for
Network wait time rises during incidents
Threads blocked on socket reads
CPU falls when network latency improves
What it usually means
The system is paying the cost of waiting for network responses, which shows up as CPU usage in the thread scheduling.
What to do next
- 1Add timeouts to all network calls
- 2Use async or non-blocking IO
- 3Add circuit breakers for slow dependencies
See what's causing your CPU
cpum.ai turns CPU, process, disk, and memory signals into plain-English explanations with evidence.
Open cpum.ai