Senior Java Backend Engineer Microservices & Payments

AJAY KUMAR

Java Backend Engineer · Microservices & Distributed Systems · 2 Yrs Experiance

Greater Noida, UP (Open to Remote/Hybrid-NCR) · +91-991******* · **********@*****.*** · LinkedIn · KEY HIGHLIGHTS

Designed & deployed 6+ production microservices (Java 17 / Spring Boot) serving 5,000+ daily users; implemented Distributed Locking (Redis) + Idempotency patterns — eliminated 100% of duplicate-payment incidents across 500+ daily transactions.

Engineered Redis caching strategy (TTL-based invalidation + session management) and rewrote N+1 JPA/Hibernate queries to batch fetches; reduced P99 API latency by 25%, sustaining sub-200ms response times under high-concurrency booking load.

Architected event-driven, fault-tolerant Stripe payment pipeline with async Webhook processing, exponential backoff retry logic, and idempotent event handling — 99.9% reconciliation accuracy, zero manual interventions.

Secured Health-tech SaaS platform with RBAC (Spring Security) + Service Discovery (Eureka) for multi-tenant data isolation across 1,000+ concurrent sessions; deployed on AWS EC2 with S3-backed storage. TECHNICAL SKILLS

Core Java: Java 11 / 17 / 8 · Collections · Multi-threading · Concurrency APIs · JVM Tuning Frameworks: Spring Boot, Spring Security (RBAC), Hibernate / JPA, Maven Distributed Systems: Microservices, Distributed Locking, Idempotency, Event-driven Architecture, Fault Tolerance, High Concurrency Databases & Caching: MySQL (Relational), MongoDB (NoSQL), Redis (Caching & Session Management) Messaging & Events: Webhooks, Async Processing, Retry Logic, Socket.io (Real-time Streaming), Cron Jobs API & Architecture: REST APIs, API Gateway, Service Discovery (Eureka), Polyglot Persistence DevOps & Cloud: Docker, Jenkins CI/CD, AWS (EC2, S3), Git Domains: Fintech Payment Systems, Health-tech SaaS PROFESSIONAL EXPERIENCE

Software Developer — Java Backend NOYT India Pvt Ltd, Greater Noida Mar 2024 – Present

Designed & developed 6+ scalable microservices using Java 17 and Spring Boot; leveraged Java Collections, Multi-threading, and Concurrency APIs to handle 500+ simultaneous booking requests with zero data races.

Implemented Distributed Locking (Redis) + Idempotency patterns to enforce data integrity across distributed booking transactions — eliminated duplicate payment failures and ensured exactly-once processing under concurrent load.

Integrated Stripe payment gateway with event-driven, async Webhook processing and exponential-backoff retry logic; achieved 99.9% transaction reconciliation accuracy with fault-tolerant, idempotent event handling and zero manual corrections.

Optimized API performance by 25% (P99 < 200ms) via Redis caching strategies (TTL-based invalidation, session management) and rewriting N+1 Hibernate queries to batch fetches; sustained throughput under peak traffic spikes.

Built real-time event streaming layer using Socket.io for live booking status updates across 5,000+ daily active sessions; architected pub/sub model for low-latency status propagation.

Containerized all microservices with Docker and automated CI/CD pipelines via Jenkins; reduced deployment cycle by ~40% and eliminated environment-drift issues across dev / staging / prod on AWS EC2.

Enforced multi-tenant data isolation using RBAC (Spring Security) with fine-grained role permissions, securing a Health-tech SaaS platform across 1,000+ concurrent tenant sessions without performance overhead. KEY PROJECTS

Holistic Health Platform — bookyourholistic.com · Health-tech SaaS · Live Production

Architected centralized API Gateway with Service Discovery (Eureka) routing requests across 4+ microservices; applied polyglot persistence — MySQL for ACID-compliant booking data, MongoDB for dynamic provider profiles — deployed on AWS EC2 / S3.

Implemented session-aware multi-tenant backend with Redis session management and complete tenant data isolation; supported 1,000+ concurrent sessions with zero cross-tenant data leakage. Scalable E-Commerce Backend — Fintech-adjacent · REST APIs · Event-driven · Microservices

Developed high-throughput REST APIs for catalog, inventory, and order management with cursor-based pagination; leveraged Java Collections and JVM-level optimizations to sustain 10,000+ SKU queries without degradation.

Automated stale-inventory cleanup via event-driven Cron Jobs; reduced orphaned DB records by 60% and improved query performance on high-volume inventory tables.

EDUCATION

MCA — Master of Computer Applications Galgotias University, Greater Noida2023 – 2025 BCA — Bachelor of Computer Applications Global Institute of IT ( CCSU), Greater Noida2020 – 2023

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