Senior Fullstack Developer, Java

November 4

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Block Labs

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Crypto • Web 3 • B2B

Block Labs is a Web3-focused builder, investor, and marketing partner for blockchain projects. The company provides end-to-end blockchain development (smart contracts, decentralized wallets, NFT exchanges, payment gateways), web3-native marketing (social management, influencer/KOL campaigns, paid media, PR, partnerships), and investment support from seed to Series A. Block Labs works with founders to accelerate growth through technical development, go-to-market strategies, and strategic capital, operating from Sofia, Bulgaria.

51 - 200 employees

Founded 2022

₿ Crypto

🌐 Web 3

🤝 B2B

📋 Description

• Design and develop backend services in Java 17+ using Spring Boot and Maven • Build and maintain microservice integrations across authentication, payments, chat, and gameplay • Implement and maintain REST and WebSocket APIs for game logic and real time communication • Integrate frontend clients (Dart, TypeScript, or similar) with backend systems • Develop and support integrations with third party platforms, payment gateways, and cashier services • Collaborate with product and backend teams to ensure seamless transaction management, wallet synchronisation, and player balance handling • Contribute to frontend modules where needed, supporting UI logic and state synchronisation • Collaborate on data modelling, schema design, and optimisation • Participate in code reviews, debugging, and performance optimisation • Ensure scalability, data consistency, and high availability across distributed systems

🎯 Requirements

• Strong proficiency in Java (17+) and Spring Boot • Experience integrating with payment systems, third party APIs, or cashier services • Familiarity with WebSocket communication and real time data exchange • Solid understanding of REST API design and microservice architecture • Experience with SQL databases, schema design, and query optimisation • Exposure to frontend development (Dart preferred, or JavaScript/TypeScript) • Knowledge of containerised environments (Docker) and CI/CD pipelines • Comfortable working in a multi repository, multi module setup • Understanding of state management, protocol-based communication, and client server synchronisation • Experience in real time multiplayer or financial transaction systems

🏖️ Benefits

• Mature, mission-driven, and low-ego culture