Debug Latency

Latency Diagnosis

Trace the FULL path from trigger to response. Latency hides in the handoffs between components.

1. Client-Side Latency (User Action → Request Sent)

Check:

• Event handler fires immediately on user action (no debounce/throttle unless intentional)
• No heavy computation blocking the main/UI thread
• Request constructed and sent without unnecessary delays
• No redundant re-renders or recomputations before sending

Common culprits:

• Heavy synchronous work on UI thread
• Unnecessary state updates triggering re-renders before the actual action
• DNS resolution on first request (cold start)

2. Network Latency (Request → Server Receives)

Check:

• Connection reuse (keep-alive, HTTP/2)
• Payload size reasonable (compress large bodies)
• CDN or edge caching for static/cacheable content
• TLS handshake overhead on new connections

Common culprits:

• No connection pooling (new TCP + TLS per request)
• Large uncompressed payloads
• Wrong region (server far from users)
• Missing CDN for static assets

3. Server Processing Latency (Receive → Response Ready)

Check:

• Database queries use indexes (check EXPLAIN)
• No N+1 query patterns
• Expensive operations are cached
• External service calls have timeouts
• No unnecessary serialization/deserialization

Common culprits:

• Missing database indexes (full table scans)
• Synchronous external API calls that could be parallel
• Lock contention on shared resources
• Logging or tracing overhead in hot paths

4. Response Latency (Server Sends → User Sees Result)

Check:

• Response size minimized (no over-fetching)
• Streaming for large responses where possible
• Client-side rendering/parsing efficient
• UI updates immediately on data arrival (no artificial delays)

Common culprits:

• Sending entire objects when client needs one field
• Waiting for all data before rendering (could stream/paginate)
• Heavy client-side processing of response data

Output

CLIENT PATH:  [action] → [handler] → [request] | Est: Xms
NETWORK PATH: [send] → [receive]               | Est: Xms
SERVER PATH:  [receive] → [process] → [respond] | Est: Xms
RENDER PATH:  [receive] → [parse] → [display]   | Est: Xms
TOTAL: ~Xms

FIXES (priority):
1. [fix] - saves ~Xms
2. [fix] - saves ~Xms

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: pvnarp
• Source: pvnarp/agent-skills
• License: MIT

Install and usage instructions live in the source repository linked above.