Russian hacker, Vladimir Leonidovitch Levin, attempted the biggest bank heist the world had ever seen via dial-up internet in 1994, Zia Hayat, Callsign CEO and founder, was hooked - armchair fraud became a real possibility. From this moment, Zia knew he wanted to play a part in stopping the bad guys and securing the internet for all. Founded In 2012, Callsign's mission has been to make Digital Identity simple and secure for everyone and everything. In that time, we've grown to over 250 employees, opened offices in UK and Abu Dhabi, been recognised as a WEF Global Innovator and our technology is being used by many of the world's leading financial institutions to keep millions of consumers safe.

But we aren't stopping here. The identity revolution has only just begun, and we are looking to hire the brightest and inquisitive minds to help us make every web, mobile and physical Interaction seamless and secure. If this sounds like you, lets chat.

As a Software Engineer at Callsign, you will design, build, and maintain components of our highly transactional Java platform. You’ll work in an Agile, fast‑paced environment, collaborating with cross‑functional teams to deliver secure, scalable, and performant software. You’ll take ownership of features from development through deployment, proactively improving code quality, reliability, and efficiency.

Responsibilities

• Design, develop, test and maintain Java‑based services and APIs.
• Write clean, testable, and maintainable code following engineering best practices.
• Understand requirements before writing code by participating in refinement sessions with peers, QA and Product to deliver high‑quality features.
• Participate in code reviews and contribute to continuous improvement.
• Perform end-to-end testing of pushed code.
• Support production deployments and troubleshoot issues with SRE/App Support.
• Identify and address technical debt and performance bottlenecks.

Requirements

• 3–6 years of commercial experience in Java development.
• Strong knowledge of Java (8+/17+), Spring Boot, and RESTful API design.
• Experience with relational databases (PostgreSQL/MySQL/Oracle) and SQL.
• Familiarity with DynamoDB or other noSQL databases.
• Familiarity with Docker, Linux, and CI/CD pipelines.
• Understanding of software testing principles (unit, integration, contract and regression).
• Understanding of OOP fundamentals and SOLID principles.
• Understanding of space and time complexity.
• Production experience of Metrics for reliable observability.
• Experience with rules engines, expression languages or workflow engines.
• Experience with orchestration and workflow patterns such as Saga, Process Manager or state machines.
• Exposure to microservices architecture, distributed caching with Redis, and event streaming with Kafka.
• Awareness of secure coding practices and application security fundamentals.
• Strong communication, analytical thinking, and collaboration skills.

Good to have :

• Familiarity with observability tools (Prometheus, Grafana, ELK, OpenTelemetry).
• Experience with message queues (Kafka, RabbitMQ).
• Basic knowledge of Kubernetes, AWS, or Terraform.
• Experience in high‑growth or startup environments.
• Exposure to crypto practices and encryption/decryption
• Understanding of distributed system patterns such as Circuit Breaker, Idempotency and Outbox
• Exposure to reactive programming (Spring WebFlux / Project Reactor) or Java Virtual Threads
• Understanding of applied cryptography (encryption, hashing, digital signatures, TLS/mTLS)

Benefits

• Private Premium Health Insurance
• Visa costs including 1 month paid hotel stay on arrival
• Annual Airfare Allowance for the home country
• 3 months full pay maternity leaves & 2 weeks full pay paternity leaves
• 25 days of annual leave + Callsign Bank Holiday (not included in holiday allowance)
• Competitive Salary
• Gratuity as EOSB