Senior Software Engineer (Java)

IntellectEU; Portugal; Remote; EUR 90,000 - 120,000; Full time

Job summary

IntellectEU is seeking a Senior Software Engineer to join our high-caliber Web3 backend team. You will own the delivery of core services powering wallet operations, asset transfers, and blockchain integrations in regulated environments.

Location: EU-remote with some overlap with EDT; you will collaborate across teams, write well-tested code, and drive architectural decisions for scalable, secure, event-driven systems using Kafka and OpenTelemetry.

Qualifications

• 7+ years of backend software engineering in regulated environments.
• Deep Java and Spring Boot expertise; comfortable with polyglot stacks.
• Strong API-first design and microservices experience.
• Proficient in asynchronous, concurrent, and multi-threaded programming.
• Track record delivering highly available distributed applications.
• Hands-on with event-driven architectures using Apache Kafka.
• CI/CD, DevSecOps practices and secure SDLC fundamentals.

Responsibilities

• Implement and operate core backend services with fault tolerance, security, and scalability.
• Build API-first services integrating blockchain networks and providers.
• Implement secure service communications using cryptographic methods and zero-trust principles.
• Operate event-driven systems using Kafka and asynchronous messaging patterns.
• Produce documentation, API specs, and runbooks; ensure high test coverage.

Skills

Java

Spring Boot

API design

Distributed systems

Kafka

CI/CD

Security

Tools

Apache Kafka

OpenTelemetry

CI/CD tooling

Job description

IntellectEU is an international technology company focused on digital finance and emerging technologies. At IntellectEU we are on a mission to become the top-of-mind fintech company. We are committed to our people and believe in building a better future with the newest technologies. We give rising talent and industry veterans the space to explore, launch ideas, and collaborate closely with our clients. With our technical hands-on experience in payments, blockchain and capital markets, there's no challenge that’s left unsolved. Over the past two decades, we have earned our expertise in financial technology, executing on hundreds of complex integrations and co-creating new digital asset platforms alongside our clients. We are looking for a Senior Software Engineer to join a high-caliber Web3 engineering team of our client. This is a deeply technical, hands‑on individual contributor role. The successful candidate will own the delivery of core backend services supporting wallet operations, asset transfers, transaction orchestration, blockchain integrations, and event‑driven workflows operating at scale within regulated financial environments.

Location - EU, remote. 5-hour overlap with EDT time is required.

Responsibilities

• Implement and operationalize core backend services with fault tolerance, security, and scalability.
• Build API‑first services integrating blockchain networks, third‑party provider solutions, and internal systems with strong consistency guarantees.
• Implement secure service communications using cryptographic signatures, key management, and zero‑trust architecture principles.
• Operationalize event‑driven systems using Apache Kafka and asynchronous messaging patterns.
• Build highly available, strongly consistent, horizontally scalable services.
• Implement robust concurrent and asynchronous processing patterns for multi‑threaded workloads.
• Integrate Web3 SDKs and libraries for on‑chain interactions, transaction signing, and state monitoring.
• Implement structured logging, distributed tracing, metrics, and OpenTelemetry instrumentation.
• Produce and maintain high test coverage via automated unit, integration, and functional testing frameworks within CI/CD pipelines.
• Produce and maintain technical documentation, API specifications, and operational runbooks.

Requirements Must Have

• 7 or more years of software engineering experience building and operating production‑grade backend systems in regulated financial or enterprise environments.
• Extensive hands‑on proficiency in Java and Spring Boot. Comfort operating across polyglot stacks.
• Deep expertise in API‑first design, RESTful service contracts, and microservices architecture patterns.
• Strong command of concurrent, multi‑threaded, and asynchronous programming models.
• Proven track record delivering highly available, strongly consistent, and distributed applications.
• Hands‑on experience building event‑driven solutions using Apache Kafka. Solid understanding of messaging patterns including pub/sub, event sourcing and saga/choreography orchestration.
• Strong understanding of CI/CD, DevSecOps practices, secure SDLC, and automated security controls.
• Hands‑on experience with OpenTelemetry, distributed tracing, and observability platforms.
• Strong technical writing skills; demonstrated ability to produce API specs and runbooks.

Nice to Have

• Extensive hands‑on proficiency in TypeScript, Node.js, and/or NestJS.
• Direct experience with Ethereum, Bitcoin, Solana, XRPL, and other distributed ledger technologies.
• Familiarity with MPC (Multi‑Party Computation), HSMs, and enterprise key management systems.
• Experience implementing Zero Trust security architecture end‑to‑end.
• Knowledge of tokenization, stablecoins, settlement systems, and digital asset operations.
• Contributions to open‑source blockchain projects or Web3 tooling.
• Experience with AI‑assisted development workflows and LLM‑powered tooling.

We guarantee

• International experience in a stable company: the company has offices in Antwerp, Leuven, Lisbon, Krakow, Kyiv, New York and operates on the market for over 15 years.
• Passionate team in an innovative casual, positive, and open work environment ready to meet your new ideas.
• Great opportunities for personal and professional development as well as the chance to change the way the business works in the financial world.
• Work where you're most productive: remote, in‑office, or hybrid options available.

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