Melodiket

A proven framework for enterprise-level application development, enabling RESTful API development and loosely coupled design through dependency injection. Particularly effective for security enhancement through Spring Security and efficient data persistence management through JPA.

Implements JWT-based authentication and Role-Based Access Control (RBAC) to securely handle user authentication and authorization. Performs security validation at the request level through filter chains and enables fine-grained access control for various endpoints.

Implemented concurrency control using Redisson-based distributed locks. To solve concurrency issues when multiple users try to book the same seat simultaneously, applied Redis-based distributed locks to ensure atomicity of seat reservations and maintain data consistency. Built a safe and reliable seat booking system even in distributed environments through Redisson's distributed lock features. Also utilized Redis as a cache to store frequently accessed data such as concert lists and seat information, reducing DB load and improving response times. Resolved synchronization issues between cache and DB through Write-Through strategy and TTL-based cache invalidation.

Wrote smart contracts in Solidity to implement automated profit distribution logic on the blockchain. Integrated Java backend with Ethereum blockchain network through Web3j to implement smart contract deployment and invocation features.

Built an IPFS node server using Node.js to store NFT photocard metadata and images in a distributed storage. Enables permanent data storage and access through IPFS's hash-based content addressing.

Resolved N+1 problems and optimized fetch joins through execution plan analysis when querying concert lists. Significantly reduced unnecessary queries to improve response times and enhanced query performance by adding appropriate indexes.

Utilized Redis as a cache to store frequently accessed data such as concert lists and seat information, reducing DB load and improving response times. Resolved synchronization issues between cache and DB through Write-Through strategy and TTL-based cache invalidation.

Applied cursor-based pagination to resolve performance issues of offset-based pagination when querying large amounts of data. Improved performance by efficiently utilizing indexes through a method that queries the next page based on the last queried ID.

Resolved concurrency issues during seat reservations using Redisson-based distributed locks. Ensured data consistency by combining MySQL transaction isolation level (REPEATABLE READ) with distributed locks, preventing race conditions when multiple users try to book the same seat simultaneously.

Implemented a token-based authentication system by combining Spring Security and JWT. Applied Role-Based Access Control (RBAC) to finely control APIs accessible based on user roles (audience, musician, venue manager). Enhanced security by implementing token expiration times and refresh token mechanisms.

Implemented a global exception handler using Spring's @ControllerAdvice to handle all exceptions in a consistent format. Defined custom exception classes and mapped appropriate HTTP status codes and error messages to provide error responses that clients can easily understand and handle.

Clearly separating responsibilities through 3-tier architecture significantly improved maintainability and scalability. Designed stable APIs with a global exception handler and security system using Spring Security.

Cleanly implemented complex business logic for concert contracts using state and strategy patterns, and gained experience applying blockchain technology to actual services through smart contract and backend integration.

We lacked sufficient investigation into blockchain transaction processing in the early stages of the project.

We didn't deeply consider real-world operational constraints such as blockchain network latency, gas costs, and transaction processing times, and failed to systematically design solutions for data synchronization issues between smart contracts and backend or rollback handling for failed transactions.

Before introducing blockchain, I will conduct performance benchmarks in real operational environments and introduce a process to compare and analyze characteristics of various blockchain networks (Ethereum, Polygon, etc.) to select the network optimized for the project.

Before deploying smart contracts, I will conduct sufficient load testing on testnets and perform analysis to predict operational costs by applying gas optimization techniques.

Considering the uncertainty that can arise from blockchain characteristics, I would like to try reviewing non-blockchain alternative solutions together and designing a hybrid architecture.