Mid-Level Java Developer

SLEM Technologies; United States; Remote; USD 90,000 - 150,000; Full time

Job summary

SLEM Technologies is seeking a Java engineer to build and maintain services for our payment products. You will work with Spring Boot and integrate MPGS and Visa Cybersource to support checkout, processing, refunds, and reconciliation, while investigating failures and ensuring data security.

You will implement endpoints, handle 3-D Secure flows, manage notifications, write SQL, and contribute tests to verify handling of approvals, declines, and errors.

Qualifications

• 2+ years of professional Java experience, preferably in fintech or payment-processing systems.
• Hands-on integration experience with MPGS and Visa Cybersource.
• Practical experience with Spring Boot and relational databases.
• Understanding of authorisation, capture, refunds, tokenisation, 3-D Secure, and reconciliation.

Responsibilities

• Implement payment endpoints and gateway integration features in Java and Spring Boot.
• Maintain authorisation, capture, void, refund, tokenisation, and 3-D Secure flows with guidance from senior engineers.
• Process gateway notifications and payment statuses; use idempotency and safe retries to avoid duplicates.
• Write SQL queries and persistence code for transaction records and settlement reconciliation.
• Add unit and integration tests for approvals, declines, timeouts, and gateway errors.
• Investigate payment defects using sanitised logs and follow secure development practices.

Skills

Java

Spring Boot

Fintech/payments

HTTP APIs

Git and tests

Tools

SQL

Docker

CI/CD

Job description

Role overview

Build and maintain Java services for payment products, using Spring Boot and practical experience with both MPGS and Visa Cybersource. Working with senior engineers, you will contribute to checkout, transaction processing, refund, and reconciliation features, while helping investigate failures and preserve the accuracy and security of financial data.

Responsibilities

• Implement payment endpoints and gateway integration features in Java and Spring Boot.
• Maintain authorisation, capture, void, refund, tokenisation, and 3-D Secure flows with guidance from senior engineers.
• Process gateway notifications and payment statuses; use idempotency and safe retries to avoid duplicate transactions.
• Write SQL queries and persistence code for transaction records and settlement reconciliation.
• Add unit and integration tests for approvals, declines, timeouts, and gateway errors.
• Investigate payment defects using sanitised logs and follow secure development practices.

Requirements

• At least two years of professional Java experience, including work on fintech or payment-processing systems.
• Hands-on integration experience with both MPGS and Visa Cybersource.
• Practical experience with Spring Boot and relational databases.
• Understanding of authorisation, capture, refunds, tokenisation, 3-D Secure, and reconciliation.
• Familiarity with HTTP APIs, idempotency, payment error handling, and safe retries.
• Awareness of PCI DSS and secure handling of payment credentials and sensitive data.
• Comfortable using Git and automated tests, with clear written communication and a collaborative approach.

Nice to have

• Experience testing gateway integrations in sandboxes and supporting go-live checks.
• Familiarity with financial ledgers, message queues, Docker, or CI/CD.