Job Summary: We are seeking a Senior Backend Engineer for a strategic project involving high-performance critical systems within the financial sector, focused on optimization and real distributed architecture. Key Highlights: 1. Participation in a high-impact initiative in the financial sector. 2. Advanced technical environment focused on quality engineering. 3. Integration into an international team with a strong technical culture. Senior Backend Engineer – High-Performance Critical Systems Madrid (northwest area) \| Hybrid model (3 days onsite) * Full-time \| Immediate start \| Strategic project An international technology firm specializing in digital transformation for large corporations is looking to hire a Senior Backend Engineer for a technically demanding project within the financial domain. This is not a position oriented toward “standard development.” Here, we speak about performance, concurrency, optimization, and real distributed architecture. The Challenge Participate in the evolution of critical platforms where code efficiency and system stability are paramount. You will work in high-concurrency environments requiring minimal latency and absolute robustness. Key Responsibilities Backend development with a strong focus on performance and scalability. Advanced programming in Python (core development, not data-related). Implementation and optimization of components in C\+\+ (Java is a plus). Design and integration of APIs in distributed environments. Working with in-memory databases (Redis and/or Valkey). Participation in architectures based on distributed computing grids (HTC, Condor, IBM Symphony, TIBCO DataSynapse, or similar solutions). Diagnosis and resolution of complex production incidents. Application of best practices: testing, technical documentation, and code quality. Proven senior-level backend development experience. Strong structural and architectural mastery of Python. Solid experience in C\+\+ focused on optimization. Practical knowledge of distributed systems and grid-style computing. Experience consuming and integrating APIs. Advanced English (C1 or equivalent). Residency in Spain and valid documentation. A university degree is not mandatory if professional experience is substantial. We seek an analytical, autonomous mind comfortable in technically demanding environments. Participation in a high-impact initiative within the financial sector. Advanced technical environment focused on quality engineering. Stable hybrid model (3 days onsite in Madrid’s northwest area). Intensive summer schedule. Integration into an international team with a strong technical culture. If you enjoy fine-tuning code down to the millisecond and are motivated by working on architectures where performance is not optional—but critical—this is your next challenge.