Full Stack / Backend Software Engineer for Mobile App (Node.js / MongoDB)

Location: Remote (India preferred) Experience: 5+ years (must have production consumer app experience) Salary Range: ₹6LPA-₹10L a year About Locus Most dating apps optimise for engagement. Locus optimises for connection. Instead of juggling endless matches, Locus allows people to focus on one meaningful conversation at a time — creating calmer, more intentional interactions and better outcomes. We are live and growing. Now we’re strengthening the backend architecture to support scale, behavioural analytics and real-time interaction reliability. This is not a typical CRUD app — our system models human interaction states. Our Architecture • Mobile App: Flutter • Backend: Node.js • Database: MongoDB • Admin Panel: React JS • Infrastructure: AWS • Realtime / Messaging integrations: (WebRTC / providers) The Role We’re hiring a senior backend engineer to take ownership of our core interaction engine. Dating apps are complex systems — two independent users performing actions that must remain consistent across devices, time and network conditions. You will design and optimise the logic behind: • likes & super-likes • mutual matching • single-active conversation rules • conversation lifecycle state • behavioural event tracking • notifications & timing logic Your work directly affects whether users feel calm and connected — or confused and frustrated. Key ResponsibilitiesCore System Logic • Design matching and interaction workflows • Prevent race conditions (simultaneous likes, match conflicts) • Maintain strict single-conversation rules • Ensure deterministic state transitions Messaging & State Management • Conversation lifecycle modelling • Message ordering & consistency • Handling reconnections & offline users • Time-based behavioural triggers Database Architecture • Design scalable MongoDB schemas • Optimise indexes & query performance • Model relational behaviour in NoSQL • Prevent duplicate or conflicting states Reliability & Performance • Reduce latency across user interactions • Debug real production edge cases • Implement idempotent APIs • Scale as user volume increases Analytics & Behaviour Tracking • Implement event instrumentation • Track funnels & user actions accurately • Ensure event reliability across devices Collaboration • Work with Flutter engineers • Support React admin panel data structures • Assist DevOps when needed Required Experience (Must Have) • 5+ years backend engineering (Node.js) • Production MongoDB schema design • Built consumer-facing applications (NOT internal dashboards) • Experience handling concurrent user actions • Strong understanding of: • race conditions • eventual consistency • idempotency • state machines • API performance optimisation • Debugging live production systems Highly Preferred • Dating, chat, marketplace, or social apps • Designed messaging or matching systems • Real-time interaction platforms • Behavioural analytics implementation • High-volume user systems Nice To Have • Caching strategies (Redis) • Queue workers / background jobs • Notification systems • Subscription / entitlement logic • Experience working with Flutter teams What Success Looks Like • Matches never duplicate or disappear • Conversations always remain consistent • Notifications arrive at the correct moment • System remains stable as users scale • New features can be added safely and quickly Why Join You won’t just build APIs — you’ll shape how people form relationships. • At Locus, engineering decisions influence real human behaviour and real outcomes.