How to Scale Real-Time Delivery Tracking for 10,000 Reconnecting Users

Engineers building real-time delivery tracking maps face a core challenge: maintaining accurate state when users lose and regain connectivity across different networks. The proposed architecture separates three distinct contracts — durable delivery state, transient room presence, and the connection layer — ensuring that truth lives in the event log, not the connection. Each delivery stream uses a monotonically increasing sequence number, allowing clients to store their last applied position and request only missed events upon reconnection, falling back to a full snapshot when gaps cannot be replayed. Versioned event envelopes enable rolling releases by letting old and new consumers coexist safely, while incompatible schema changes require explicit new event types rather than silent field reuse. The result is a system where dropped connections delay updates but cannot corrupt state, and duplicate events waste bandwidth but cannot reverse progress.