WebSocket Reliability Engineering

The Challenge

The platform relied on WebSocket and XMPP connections for real-time messaging and presence. Users frequently experienced dropped connections, missed messages, and inconsistent state — especially on mobile networks or during server deployments. Support tickets about "messages not arriving" were a top complaint.

The real-time layer lacked observability: when issues occurred, the team was debugging blind.

The Approach

I tackled this from two angles — reliability engineering and observability:

Connection Reliability

• Exponential backoff with jitter for reconnection, preventing thundering herd on server recovery
• Connection state machine — a finite state machine managing connected/disconnected/reconnecting states, replacing scattered boolean flags
• Heartbeat monitoring — client-side heartbeat detection with configurable thresholds, triggering proactive reconnection before the user notices
• Message queue with replay — queued outbound messages during disconnection, replayed on reconnect with deduplication

Observability

• Splunk dashboards tracking connection lifecycle events, reconnection rates, message delivery latency, and error distributions
• Client-side telemetry — lightweight instrumentation reporting connection health metrics without impacting performance
• Alerting — configured alerts for anomalous reconnection spikes or message delivery degradation

Execution

The reliability improvements were rolled out incrementally behind feature flags, with each change validated against Splunk metrics:

1. Deployed the connection state machine and monitored reconnection patterns
2. Added heartbeat monitoring and measured the reduction in "zombie connections"
3. Implemented the message queue and tracked message delivery success rates
4. Built dashboards and shared them with the broader engineering and support teams

Results

• 99.9% connection reliability — up from approximately 97%, measured over a 90-day window
• Reconnection time dropped from 30s average to under 2s — users barely noticed interruptions
• 70% reduction in connectivity-related support tickets within the first quarter after rollout
• Real-time observability — engineering and support teams could diagnose issues in minutes instead of hours