Senior Software Engineer (Telco & Comms)

About Callsign

Role overview

Key responsibilities

• Write production-ready code and understand the pipeline and artifacts used to ship it.
• Write low-level designs for implementation and represent the team in architecture reviews.
• Threat-model features; design authentication, authorization, and data handling from the start.
• Instrument services before release, take on-call turns, and drive faults to root cause.
• Identify technical gaps, propose fixes with costs and benefits, and use AI tooling.
• Mentor engineers, uphold standards for testing and error handling, and interview candidates.

Requirements

• Eight or more years with Java 17+, Spring Boot, and Spring Security; diagnose JVM and Spring issues using thread dumps, heap dumps, and traces.
• Design and operate client-facing microservices with API versioning and unit, integration, contract, and load testing.
• Design for failure and scale with idempotency, retries, circuit breakers, and caching; diagnose bottlenecks with data.
• Strong relational modeling and query design, primarily MySQL, including schema and index tuning under load.
• Apply OWASP Top 10, authentication, authorization, secrets management, and secure data-handling practices.
• Write implementation-ready designs and review peers' designs.
• Deploy and operate services on Kubernetes with Docker, Helm, AWS, and CI/CD; debug failed deployments.
• Own changes from design through on-call and instrument services to detect faults before clients report them.

Good-to-have experience

• Reactive Java in production, including Spring WebFlux, Project Reactor, RxJava, or Vert.x.
• MNO and telco integrations, including number insight, SIM swap, or other network signals.
• OAuth 2.0, JWT, SAML, FIDO, or WebAuthn.
• Banking, payments, or regulated-industry experience, including audits or client security reviews.
• SLIs, SLOs, error budgets, production Kafka, or Terraform.

Benefits

• Private premium health insurance and visa costs, including a one-month paid hotel stay on arrival.
• Annual home-country airfare allowance.
• Three months of full-pay maternity leave and two weeks of full-pay paternity leave.
• Twenty-five days of annual leave plus a Callsign bank holiday, and gratuity as EOSB.
• Competitive salary.