Hey, I'm Abhimanyu

• Engineered Zero Trust–compliant PAYIN/PAYOUT/ADMIN APIs, enforcing authentication and authorization on every request using OAuth2 + OIDC, independent of network or service origin
• Implemented role-based (RBAC) and scope-based authorization using JWT claims, enabling fine-grained access control for admin, merchant, and system-level operations
• Designed user tokens and service tokens with strict audience (aud) restriction and short TTLs, ensuring APIs accepted tokens only from intended callers and minimizing blast radius on compromise
• Secured service-to-service communication using OAuth2 Client Credentials flow, eliminating shared secrets and enabling identity-centric machine authentication
• Implemented JWT validation at the application layer, verifying signature, issuer (iss), audience, scopes, and expiry locally via JWKS without runtime IdP dependency
• Enforced end-to-end encryption using TLS 1.2+ for all API traffic, with optional payload-level encryption using public/private key pairs for sensitive payment and PII fields
• Integrated cryptographic key rotation for JWT signing and service encryption keys, supporting multiple active keys via kid headers and seamless rotation without downtime
• Hardened APIs with rate limiting, contextual identity-based logging, and audit trails, ensuring all access was traceable to a user or service identity rather than IP address
• Zero Trust security guarantees across Kafka-driven, event-based payment workflows
• Implemented Debezium + Outbox pattern ensuring atomic message delivery and DB consistency
• Deployed Elasticsearch search layer, cutting report latency by 80%
• Built Storm + Kafka fraud-detection pipeline, processing 15K+ events/s

• Architected and developed modular microservices for cart, checkout, payment, and delivery
• Leveraged RabbitMQ for notification delivery and Redis for session storage and rate limiting
• Enabled Elasticsearch-based search on menu items and restaurant metadata
• Integrated OAuth2/JWT based login and RBAC with Spring Security
• Wrote extensive test coverage with JUnit5 & Mockito; integrated with Postman automated suites
• Designed API contracts and documented all endpoints using Swagger/OpenAPI
• Conducted query profiling and optimization to improve DB performance and resolve timeouts
• Guided junior developers and contributed to code reviews, refactoring, and mentorship

• Developed backend modules for the government training scheme tracking
• Used Spring MVC and Hibernate with custom HQL/native SQL for complex queries
• Designed JasperReports-based dynamic PDF generation and automated email delivery
• Configured role-based access control and user session management
• Ensured data integrity, input validation, and exception handling across all modules

• Developed REST APIs for a Doctor Appointment Booking System with dynamic slot scheduler
• Integrated payment gateway APIs with support for refunds and transaction audits
• Fixed N+1 query issues and used Hibernate second-level caching to improve performance
• Designed and deployed services to AWS EC2, managed AMIs and environment configurations
• Built internal tools for doctor availability tracking and admin reporting

• Contributed to social platform "SkillThrust" with features like chat, geolocation, and reviews
• Used Google Maps API for live tracking and calendar scheduling for events
• Implemented OTP-based registration, social login (Google/Facebook), and access control
• Created validation utilities to handle anti-spam, input sanitization, and secure storage
• Supported deployment using AWS EC2/S3, worked closely with the frontend team (JSP/jQuery)

• Deliver robust, scalable, and secure software solutions for real-world business needs.
• Continuously learn and adopt new technologies to stay at the forefront of web and backend development.
• Contribute to open-source projects and the developer community.
• Mentor and collaborate with other engineers to foster a culture of growth and innovation.

"Abhimanyu is a highly skilled engineer who consistently delivers quality work on time. His expertise in Java and microservices is top-notch."

- Former Manager, Analytiq Business Ventures

"A pleasure to work with, always proactive and detail-oriented. Highly recommended for any challenging project."

- Team Lead, Appizum Technology

• Custom Web Application Development - Full-stack solutions using Java, Spring Boot, React, and Next.js
• SEO & Performance Optimization - Improve search rankings and site speed for better user experience
• API & Backend Engineering - RESTful APIs, GraphQL, microservices with Java, Spring Boot, Node.js
• Cloud & DevOps Consulting - AWS deployment, Docker containerization, CI/CD pipelines (GitHub Actions, Jenkins)
• UI/UX Design & Responsive Frontend - Modern, mobile-first designs with React, Next.js, and Tailwind CSS [using AI-based IDE]
• Technical Mentoring & Code Review - Best practices, architecture guidance, and code quality improvement
• Kafka & Event-Driven Architecture - Real-time data streaming, message queues, and async processing
• Data Engineering & ETL Pipelines - Build scalable data pipelines with Apache Kafka, Spark, Flink, Debezium CDC, Airflow, Python, and real-time stream processing
• Database Design & Optimization - MySQL, PostgreSQL, MongoDB, Redis, Elasticsearch setup and tuning
• Security Implementation - OAuth2, JWT authentication, API security, OWASP compliance
• Microservices Architecture - Design, development, and deployment of scalable microservices
• Legacy System Modernization - Migrate monolithic applications to modern tech stacks
• Technical Documentation - API documentation, system architecture diagrams, developer guides

Dear Hiring Manager,

I am writing to express my strong interest in the Senior Java Backend Engineer / Technical Architect position at your organization. With over 7 years of hands-on experience designing and developing high-performance, event-driven systems, I am confident in my ability to contribute to your team's success and drive impactful technical solutions.

Throughout my career, I have specialized in building scalable microservices architectures, implementing Kafka-based real-time data pipelines, and delivering secure, production-grade APIs using Spring Boot 3, Spring Security 6, and Hibernate 6. My expertise spans the full software development lifecycle—from architecture design and implementation .

Key highlights of my experience include:

• Zero Trust Security Implementation: At Analytiq Business Ventures (Eazypaymentz), I engineered OAuth2 + OIDC compliant PAYIN/PAYOUT/ADMIN APIs with role-based and scope-based authorization, JWT validation, end-to-end TLS encryption, and cryptographic key rotation—ensuring secure, traceable access across all payment workflows.
• Real-Time Event Processing: Built a fraud-detection pipeline processing 15K+ events/second using Apache Storm, Kafka, and Elasticsearch, achieving sub-second latency with exactly-once semantics and comprehensive monitoring via Prometheus and Grafana.
• Microservices Architecture: Designed and developed modular e-commerce and food delivery systems at Appizum Technology, leveraging RabbitMQ for notifications, Redis for caching and rate limiting, and Elasticsearch for advanced search capabilities—resulting in 80% reduction in report latency.
• AI-Enhanced Trading Platform: Achieved 100% win-rate (59/59 trades) by building a 6-model ensemble ML system integrated with Spring Boot 3 microservices, MongoDB, Redis, Kafka, and FreqTrade for live trading with sub-3-second latency.
• Full-Stack SaaS Development: Architected Learn Ink, a multi-tenant LMS platform with Kafka-based notifications, CQRS pattern implementation, payment gateway integration (Stripe + Razorpay), and real-time analytics using Elasticsearch.

I am proficient in Java (17/11/8), Python, Rust, and C/C++, with deep expertise in the Kafka ecosystem (Kafka Connect, Debezium CDC, Schema Registry, Kafka Streams), Spring Boot 3, Docker, and AWS. I follow SOLID principles, Test-Driven Development (TDD), and domain-driven design (DDD) to ensure maintainable, scalable, and robust solutions.

Beyond technical skills, I am passionate about mentoring junior developers, conducting thorough code reviews, and fostering a culture of continuous improvement. I thrive in collaborative environments where innovation, quality, and performance are prioritized.

I am excited about the opportunity to bring my expertise in backend engineering, system architecture, and real-time data processing to your team. I am confident that my technical depth, problem-solving mindset, and commitment to excellence align well with your organization's goals.

Thank you for considering my application. I look forward to the opportunity to discuss how I can contribute to your team's success.

Sincerely,

Abhimanyu Kumar