Senior Software Engineer – Telco & Communications

About the role

Founded in 2012, Callsign aims to make digital identity simple and secure for everyone. The company protects millions of consumers through technology used by leading financial institutions. As a Senior Software Engineer you will help secure web, mobile and physical interactions for telco and communications services.

Key responsibilities

• Write production‑ready Java code, design low‑level specifications and represent the team in architecture reviews.
• Threat‑model features, design authentication/authorization, instrument services before release and drive faults to root cause.
• Mentor engineers, enforce testing standards, and participate in candidate interviews.
• Own the full lifecycle of changes from design through on‑call, ensuring observability and reliability.

Required profile

• 8+ years of experience with Java 17+, Spring Boot, Spring Security and debugging JVM issues.
• Strong background designing, operating and scaling microservices on Kubernetes, Docker, Helm and AWS.
• Expertise in relational data modeling and query optimisation in MySQL.
• Experience with security design (OWASP Top 10, secrets management) and implementing OAuth 2.0, JWT, SAML, FIDO or WebAuthn.

Required skills

• Java 17
• Spring Boot
• Spring Security
• Microservices architecture
• API versioning
• MySQL
• Kubernetes
• Docker
• Helm
• AWS
• CI/CD pipelines
• OWASP Top 10
• OAuth 2.0
• JWT
• SAML
• FIDO
• WebAuthn
• Kafka
• Terraform
• Reactive Java (Spring WebFlux, Project Reactor, RxJava, Vert.x)

What we offer

• Private premium health insurance
• Visa costs including one‑month paid hotel stay on arrival
• Annual airfare allowance for the home country
• 3 months fully paid maternity leave and 2 weeks fully paid paternity leave
• 25 days annual leave plus Callsign bank holidays
• Competitive salary and gratuity as EOSB