Orbit Social Hub — Real-time Messaging Architecture

Context

A B2B communications product needed to consolidate inbound channels (web chat, social DMs, internal notifications) into one operator surface — without losing the real-time feel that made the product worth using.

Approach

• WebSockets at the edge, Redis Streams in the middle. A clean split between fan-out and durability.
• Idempotent everything. Every event has a stable hash; replays are safe and observed.
• Backpressure as a feature. When an operator gets behind, the UI tells them and the system protects itself instead of dropping silently.

Engineering decisions worth talking about

• A connection broker that holds tenant state in memory but writes session checkpoints to Redis every few seconds — fast normal path, no surprises during pod rotation.
• Lag and error-budget metrics piped directly into the operator UI: the team that runs the system sees what the system feels.
• A small library that lets product engineers add new event types without touching the realtime substrate.

Outcome

The system handled launch spikes that would have crushed the previous architecture. The on-call rotation became uneventful. The product kept the live, snappy feel users expected.