Zeta is seeking a Software Development Engineer II - Backend to build large-scale transaction processing systems for payment networks and develop applications for banks. Responsibilities include building scalable and secure payments platforms, gathering requirements from product teams, implementing advanced cryptography, analyzing large datasets, developing low-level infrastructure for network performance, identifying problem patterns, and researching new technologies. The role requires a Bachelor's/Master's degree in engineering with over 3 years of experience in enterprise systems, particularly with large-scale Java applications, distributed systems, scalability, availability, relational and NoSQL databases, concurrency, memory allocation, GC, IaaS clouds, and message brokers.