Overview

My client is looking for 3 Senior Backend Engineers to join the team on a 12 month contract. As a Backend Software Engineer, you''ll design, build, and operate Java-based backend services that power messaging security capabilities. You''ll own solutions end-to-end from implementation and testing through deployment, monitoring, and production support.

This role is adecuado for a strong backend engineer who enjoys working with distributed systems, APIs, cloud-native technologies, and large-scale messaging infrastructure while solving complex security challenges.

Responsibilities

Design, develop, and maintain backend services using Java and modern engineering practices

Build security capabilities that detect and prevent spam, phishing, malicious links, malicious attachments, and messaging abuse

Work within a large existing Java codebase and contribute to long-term platform improvements

Design and evolve APIs, ensuring strong developer experience and maintainable integration patterns

Collaborate with messaging platform teams to integrate security controls into core messaging workflows

Participate in system design discussions, evaluating solutions for scalability, reliability, and security

Own services end-to-end, including deployment, monitoring, alerting, troubleshooting, and operational support

Investigate production incidents, perform root cause analysis, and implement preventative solutions





Improve service maturity through automated testing, observability, and continuous delivery practices

Support the migration of legacy consumers from database-driven integrations to modern API-based solutions

Required

Strong experience building backend applications in Java (Java 17+ preferred)

Experience developing and operating production services

Ability to work effectively within large, established codebases

Experience with microservices and distributed systems

Familiarity with Kafka or similar messaging/streaming technologies

Experience designing and consuming REST APIs

Strong understanding of software engineering best practices, including testing, code reviews, and CI/CD

Ability to work independently and take ownership of technical solutions

Professional English communication skills

Preferred

Spring Boot or DropWizard

AWS (EKS, S3, and related services)

GitLab CI/CD and deployment orchestration tools

OpenAPI specifications and API lifecycle management

Grafana, Loki, OpenTelemetry, and distributed tracing

Experience with high-throughput messaging systems

GraphQL

Security engineering, fraud prevention, abuse detection, or application security experience

Understanding of spam detection, phishing protection, malicious file scanning, or link security

Interest in AI/ML applications for security and threat detection

📌 Senior Java Software Engineer (Distributed systems) (Madrid)
🏢 Salt
📍 Madrid