Backend Security Engineer for Controlled Android Home/Away MQTT + Socket.IO Lab Environment

We need a senior backend/security engineer to build a controlled defensive lab server for two authorized Android applications. The system uses QR-based provisioning, Socket.IO/WebSocket settings flow, MQTT app/admin clients, device roles, group pairing, heartbeat/status messages, and redacted runtime logging. The objective is documentation, compatibility testing, and defensive research only. Required skills: Node.js or Python, MQTT, Socket.IO/WebSocket, TLS/certificates, Docker/Linux, Android logcat analysis, secure logging, protocol documentation, and basic cryptography concepts such as AES-GCM and Ed25519. Deliverables: Lab server, MQTT broker configuration, QR/provisioning compatibility research, Home/Away pairing logs, redacted event dashboard, Docker deployment, security boundary document, and handoff documentation.