Java Backend Engineer (IM Server)

Responsibilities

1. Design & implement IM server.
2. Develop video/audio conferencing modules.
3. Build file management.
4. Implement calendar & scheduling: events, invitations, conflict detection, reminders, external integration.
5. Solve high-concurrency, low-latency, high-availability challenges.
6. Design distributed components: message routing, push, offline messages, data consistency.
7. Collaborate with product/client/infra teams on APIs & data models.
8. Performance tuning, capacity planning, fault-tolerance for core services.
9. Troubleshoot production issues, root cause analysis, monitoring & alerting.
10. Code reviews, documentation, knowledge sharing.

Requirements

1. Bachelor's degree or above in Computer Science or related fields; 3+ years Java backend.
2. Strong Java, concurrency, networking, JVM tuning.
3. Familiar with WebSocket/MQTT/SIP/WebRTC signaling is a plus.
4. File storage, access control, or calendar logic experience preferred.
5. Solid system design; high-traffic, low-latency experience.
6. Strong problem-solving, online debugging, performance optimization.
7. Good communication, ownership, responsibility.