Senior/Lead Java Developer – Payment Systems

(High-Throughput, Concurrent Architecture)

Department: Payments Technology

Location: Toronto, Canada

Work Authorization: Authorized to work in Canada

Experience: 10–15 years

About the Role

We are seeking a seasoned Java engineer with deep, battle-tested experience building mission-critical, high-throughput payment systems. This role owns technical design decisions for concurrency, scalability, and correctness in systems processing large transaction volumes.

Required Skills & Experience

● 10–15 years of Java development, with 5+ years specifically in high-concurrency, transactional, or financial systems.

● Core Java 17 — deep expertise in Concurrency Utilities (java.util.concurrent: ExecutorService, CompletableFuture, CountDownLatch, Semaphore, ConcurrentHashMap, Atomic classes, Locks).





● Strong understanding of multithreading concepts: thread pools, synchronization, deadlocks, race conditions, memory visibility (JMM).

● Experience building transactional, high-volume systems (payments, banking, trading, or e-commerce checkout).

● Hands-on experience with Spring Boot / Spring Framework (Spring Batch, Spring Integration a plus).

● Robust SQL and experience with RDBMS (PostgreSQL, Oracle, MySQL) under high-concurrency write loads.

● Implement and consume REST APIs for internal and third-party payment integrations.

● Hands-on ownership of Kafka or equivalent at scale — partition strategy, consumer scaling, exactly-once delivery guarantees.

📌 Senior Java Software Engineer (Toronto)
🏢 Robotix Technology Solutions
📍 Toronto