🚀 Bank Management System | Spring Boot Backend Project In this video, I am sharing my complete backend project developed using Spring Boot, Java, and MySQL. This project is designed to simulate real-time banking operations. It allows users to create accounts, manage balances, and perform transactions through REST APIs. -->The application is built using a layered architecture: -->The Controller layer handles client requests -->The Service layer contains all business logic -->The Repository layer interacts with the database using JPA -->I have implemented features like account creation, fetching account details, updating and deleting accounts. Along with this, core banking functionalities like deposit, withdrawal, and fund transfer are also implemented. The project also includes transaction tracking, where every operation is stored in the database for record purposes. This video mainly focuses on explaining the code structure and how different components of the application are connected. #SpringBoot #Java #BackendDevelopment #Projects #Learning

I’m excited to share my latest project — a Full Stack Online Banking System built using Spring Boot and MySQL 🚀 This project simulates core banking functionalities and helped me understand how real-world applications manage data and handle backend logic. The application allows users to securely register and log in, manage their profile, check their account balance, and transfer money to other users using their username. The transfer feature includes proper validations such as verifying whether the receiver exists, ensuring sufficient balance, and automatically updating the balance after a successful transaction. On the backend, I used Spring Boot to develop REST APIs and handled data persistence using MySQL. The frontend is built using HTML, CSS, and JavaScript, with seamless integration achieved through the Fetch API. 💻 Tech Stack: Java | Spring Boot | MySQL | HTML | CSS | JavaScript This project gave me hands-on experience with: REST API development Database integration Frontend-backend communication Implementing real-world business logic I’m currently working on adding transaction history and improving security features. 🎥 Demo video attached below ⬇️ 🔗 GitHub Repository: https://lnkd.in/gVuSH4Ki I would appreciate any feedback or suggestions! 😊 #Java #SpringBoot #FullStack #WebDevelopment #Projects #Learning #Backend #MySQL #GitHub

Another weekend side project. I built Yeu-Pay, a fintech REST API to explore the core mechanics of digital ledger systems and financial workflows. What I focused on : Authentication RSA-signed JWTs with Spring Security for stateless, verifiable identity Ledger design Clear modeling of Accounts, Transactions, Payments, and Invoices with enforced invariants Transaction integrity Atomic operations and consistency across related financial updates Card Provisioning Virtual card issuance with controlled balance and lifecycle states Persistence PostgreSQL + Flyway for explicit, versioned schema evolution Observability Actuator for visibility into system health and metrics Stack Java 21, Spring Boot, Spring Security, PostgreSQL, Docker Compose, Open to feedback, suggestions, or discussion. Repository: https://lnkd.in/dnhVA8cq #FinTech #BackendEngineering #SoftwareEngineering #Java #SpringBoot #SystemDesign #APIDesign #PostgreSQL #Docker #CloudNative

Day 3 of Building an Offline UPI Payment System with Spring Boot Today I implemented idempotency in the payment flow using a unique requestId, while also studying the importance of concurrency handling in payment systems. What was added: • Duplicate payment requests are detected and blocked • Prevents double debit during retries or network interruptions • Proper 409 CONFLICT response handling • Custom exception flow for cleaner API behavior • Initial understanding of how concurrent duplicate requests can impact transactions Why this matters: In payment systems, retries and simultaneous requests are common. Without idempotency and concurrency safeguards, the same transaction can be processed multiple times. Current implementation works, but there is room to improve: Areas of improvement: • Return the original transaction response instead of only throwing duplicate error • Strengthen concurrent request handling with DB constraints / locking strategies • Add request payload validation for reused requestId • Introduce expiry/cleanup strategy for old idempotency keys • Improve observability with logs and audit trails Next step: I’ll be upgrading this into a more production-ready payment flow by improving concurrency safety and returning previous transaction state on retries. Built with: -Spring Boot -Spring Data JPA -H2 -REST APIs -Java Reliable backend systems are built by handling retries, race conditions, and edge cases not just successful requests. #Java #SpringBoot #BackendEngineering #Concurrency #Payments #SystemDesign #RESTAPI #SoftwareEngineering #LearningInPublic #Fintech

Started building an offline-first UPI payment system in Java + Spring Boot. The core problem: digital payments fail when internet drops. Most solutions assume connectivity. This one doesn't. Day 1 focused on foundations- Account and Transaction models, initial settlement logic, REST APIs for testing, and H2 for rapid prototyping (PostgreSQL planned next for persistent storage and scale). But the more interesting work was defining the real engineering challenges: • How do you prevent the same payment from being processed twice when multiple relay devices forward it simultaneously? • How do you ensure an intercepted payment packet from yesterday cannot be replayed today? • How do you route payment data through untrusted devices without those devices being able to read it? None of that is implemented yet. But clear problem definition is exactly how Day 1 should end. #Java #SpringBoot #SystemDesign #FinTech #BuildInPublic #coding #springai

I am excited to share a major milestone in my transition into Java Backend Development! 🚀 Before jumping straight into powerful frameworks, I wanted to deeply understand how enterprise architecture and build tools actually work under the hood. So, I built VaultBank—a fully functional, persistent Banking CLI application written in pure Java. Instead of writing a single script, I structured this project exactly how a real-world enterprise backend is designed. Here are the key technical concepts I implemented: 🔹 Maven Multi-Module Architecture: Designed a Parent POM to manage dependencies for separated core (business logic) and cli (user interface) modules. 🔹 Separation of Concerns: Isolated the strict banking rules and data state from the terminal interface using a dedicated Service Layer. 🔹 Data Serialization & File I/O: Integrated Google Gson to deserialize/serialize Java objects, ensuring account balances and transaction histories survive application restarts via a database.json file. 🔹 Automated Regression Testing: Wrote JUnit 5 tests in an isolated src/test environment to mathematically prove the banking logic is flawless before every build. 🔹 Fat JAR Packaging: Used the Maven Shade Plugin to bundle the application into a standalone, executable JAR file. Taking the time to build this without Spring Boot gave me a profound appreciation for what Maven actually does—from dependency management and the build lifecycle to keeping production code perfectly separated from testing logic. Now that the foundation is rock solid, the next stop is turning this architecture into a REST API with Spring Boot! ☕💻 #Java #BackendDevelopment #Maven #SoftwareEngineering #CareerTransition #JUnit #LearningInPublic

We had to switch payment gateways last year. The actual payment logic? Didn't change. Same amount, same customer, same order. What broke everything was this: Service A wanted different JSON format: Service B wanted different JSON format Same data. Completely different shape. And both want the amount in cents, not dollars. And both have their own status codes in the response — Service A returns "succeeded", Service B returns "captured" our service used 0 and 1. Both mean SUCCESS on our end. So we ended up with two DTOs, two mappers, and two places to break. I got tired of this and built a library that handles it differently. You just define the mapping once in a config file. Want to switch to Service A? Change one word. That's it. But the part I'm most happy with is transforms. The transforms handle the messy parts. Dollar to cents, status code normalization, phone masking — you register them once and reuse across every mapping. Works on the response side too. Their status codes map back to yours automatically. No new DTOs. No new mappers. Just a config file. I know this isn't a groundbreaking computer science problem, but it's the kind of thing that wastes hours every few months in almost every backend project I've seen. Built it in Spring Boot. Happy to share the repo if anyone wants to take a look or give feedback. Here is repo link if you want to use it: https://lnkd.in/geYginqf #Java #SpringBoot #Backend #OpenSource

𝐖𝐡𝐚𝐭 𝐡𝐚𝐩𝐩𝐞𝐧𝐬 𝐢𝐟 𝐚 𝐩𝐚𝐲𝐦𝐞𝐧𝐭 𝐀𝐏𝐈 𝐢𝐬 𝐜𝐚𝐥𝐥𝐞𝐝 𝐭𝐰𝐢𝐜𝐞? Without proper handling, it could result in duplicate transactions. That’s where Idempotency comes in. An API is idempotent if making the same request multiple times produces the same result. In real-world systems like payments, we use Idempotency Keys. A unique key is sent with each request. If the same request is received again with the same key, the server returns the previous response instead of processing it again. This ensures: No duplicate transactions Safe retries during network failures Consistent system behavior Idempotency is critical for APIs that involve financial operations, order creation, or any non-repeatable action. Reliable systems are not just about handling success. They are about handling retries safely. 𝑯𝒂𝒗𝒆 𝒚𝒐𝒖 𝒆𝒗𝒆𝒓 𝒕𝒉𝒐𝒖𝒈𝒉𝒕 𝒂𝒃𝒐𝒖𝒕 𝒉𝒐𝒘 𝒅𝒖𝒑𝒍𝒊𝒄𝒂𝒕𝒆 𝒓𝒆𝒒𝒖𝒆𝒔𝒕𝒔 𝒂𝒓𝒆 𝒉𝒂𝒏𝒅𝒍𝒆𝒅 𝒊𝒏 𝒃𝒂𝒄𝒌𝒆𝒏𝒅 𝒔𝒚𝒔𝒕𝒆𝒎𝒔? #Java #BackendDevelopment #APIDesign #SystemDesign #Microservices

🚨 Duplicate requests can break your system Real scenario: Payment API was called twice due to network retry 💥 Result: Double payment 😬 ✅ Solution: Implemented idempotency - Used unique request ID - Stored request state in DB 💡 Takeaway: APIs should be safe for retries. Especially for payments, orders, critical operations. #Java #SpringBoot #BackendDevelopment #SoftwareEngineering  #Microservices #JPA #RESTAPI  #DeveloperLife #CareerGrowth

Started Day 2 on my offline-first UPI payment system in Java + Spring Boot. Today’s focus was moving beyond basic money transfer APIs into something real products need: transaction history. Built a recent transactions endpoint that returns the last activity for a user instead of dumping raw database rows. Also started shaping responses through DTO mapping so customers only see relevant data like amount, status, counterparty, and transaction type (Sent / Received) — not internal fields. One underrated part of backend development: debugging response serialization, mapping layers, and edge cases often takes more effort than writing the endpoint itself. That’s where real learning happens. Current progress: ✅ Account creation API ✅ Payment transfer API ✅ Custom exception handling ✅ Transaction history feature in progress ✅ DTO-based response design Next steps: Finish transaction history cleanly Add timestamps JWT auth layer Idempotency for duplicate payment prevention PostgreSQL migration from H2 Building with a product mindset, not just CRUD. #Java #SpringBoot #BackendDevelopment #SystemDesign #FinTech #BuildInPublic #backenddev #SpringAI #SpringdataJPA #microservices