11/11/2026 updated
100 % available
Backend Engineer (Java / Spring) | Fintech & Blockchain Specialist
Sofia, Bulgaria
Only remote
BA Computer ScienceAbout me
I spent four years on Java and Spring in fintech and later led the backend of a crypto on-ramp with KYC and SEPA payments. Money-moving systems where correctness matters are what I know best.
Java (Programming Language)Amazon Web ServicesSpring FrameworkBlockchainTypeScriptBackendBackend ProgrammingBlockchain PlatformsNestJSFintech
Java & Spring Development
Over 4 years of enterprise Java and Spring backend development, building and maintaining backend services for banks, developing REST APIs and integrations with existing banking systems on relational databases.
TypeScript & Node.js / NestJS Backend
Design and implementation of scalable NestJS backends, including KYC verification provider integrations and SEPA-based payment processing for fintech products.
Go & Real-Time Systems
Development of real-time game servers in Go over WebSockets, utilizing Redis streams for inter-service communication in high-concurrency environments.
Payments & KYC Integration
End-to-end implementation of fiat-to-crypto payment services, SEPA payment processing, and integration of KYC provider solutions for regulated fintech platforms.
Blockchain & Web3 Engineering
Ownership of backend API components and database schemas for lending protocols, real-time tracking of user rewards, and building blockchain indexers for Ethereum protocols.
Cloud & Infrastructure
Working knowledge of AWS and GCP cloud platforms, Postgres and Redis databases, and WebSockets for real-time data streaming.
Frontend Technologies
Practical experience with Next.js and React for full-stack contributions, as well as Solidity for smart contract interaction.
Machine Learning Platform Development
Building backend and cloud components for a machine-learning platform predicting NFT prices, including indexers for multiple Ethereum protocols feeding the models.
Over 4 years of enterprise Java and Spring backend development, building and maintaining backend services for banks, developing REST APIs and integrations with existing banking systems on relational databases.
TypeScript & Node.js / NestJS Backend
Design and implementation of scalable NestJS backends, including KYC verification provider integrations and SEPA-based payment processing for fintech products.
Go & Real-Time Systems
Development of real-time game servers in Go over WebSockets, utilizing Redis streams for inter-service communication in high-concurrency environments.
Payments & KYC Integration
End-to-end implementation of fiat-to-crypto payment services, SEPA payment processing, and integration of KYC provider solutions for regulated fintech platforms.
Blockchain & Web3 Engineering
Ownership of backend API components and database schemas for lending protocols, real-time tracking of user rewards, and building blockchain indexers for Ethereum protocols.
Cloud & Infrastructure
Working knowledge of AWS and GCP cloud platforms, Postgres and Redis databases, and WebSockets for real-time data streaming.
Frontend Technologies
Practical experience with Next.js and React for full-stack contributions, as well as Solidity for smart contract interaction.
Machine Learning Platform Development
Building backend and cloud components for a machine-learning platform predicting NFT prices, including indexers for multiple Ethereum protocols feeding the models.
Experience
Professional experience5 - 10 years
Freelancer since2024
Languages
BulgarianNative speakerEnglishFluent
Project history
Built a real-time game server in Go over WebSockets with Redis streams between services. Every hand settles to an external ledger (USDC on Base) before the next one is dealt, with a 24-hour fallback for players to recover funds. Platform went live in summer 2026 with approximately 2,000 monthly players and up to 700 playing simultaneously.
Delivering for several client projects simultaneously, working directly with clients and turning business requirements into technical solutions. Taking part in architecture decisions across different backend stacks, working with startups and early-stage teams, and owning product areas end to end including design, implementation, deployment and long-term maintenance.
Led end-to-end development of a fiat-to-crypto payments service and delivered a fully working MVP in five months. Designed and built a scalable NestJS backend integrating KYC verification providers and SEPA-based payment processing.