Senior Software Engineer – Back End

About the role

Tillster, headquartered in San Diego, CA, is the global leader in digital ordering and customer engagement solutions. We develop innovative self-service, ordering, and payments solutions for various POS systems, covering over 90% of multi-unit restaurants.

Responsibilities

• Own and re-architect the payment-terminal platform on the kiosk platform: authorize, capture, void, refund, reversal, settlement (EOD), and reconciliation.
• Design the plugin contract and lifecycle for the existing PayTerminal SPI, including discovery/registration, versioning, backward compatibility, capability negotiation, dependency isolation, per-integration configuration, and secrets management.
• Build an integration test and certification harness to validate, simulate, and regression-test new integrations before they touch real hardware.
• Design platform-wide patterns for correctness in money movement, including idempotency, transaction recovery, timeouts, heartbeat/health, concurrency, and reconciliation.
• Partner with security/QSA on audits and drive architecture and design reviews, setting technical direction for the integration layer and mentoring engineers building integrations.
• Implement new terminal integrations end to end, from byte-level protocol to the high-level PayTerminal API, working directly with serial and USB transports.
• Debug live hardware, including protocol traces, terminal logs, packet captures, and vendor certification cycles.

Requirements

• 6+ years of back-end engineering with strong Java (Maven/Java on Spring).
• Experience designing extensible / plugin / SPI-based architectures.
• Hands-on low-level device and protocol experience: serial and/or USB communication and binary protocol implementation.
• Demonstrated experience with direct payment-terminal / POS integration (Verifone, Ingenico, Adyen, Shift4, FreedomPay, SIX, Nepting, SiTef, Redsys, Worldpay, etc.).
• Clear understanding of the card transaction lifecycle, PCI-DSS boundaries, tokenization, and TLS/mTLS in production.
• Track record of technical leadership: leading designs, setting standards, and mentoring engineers.

Qualifications

• Strong grasp of the card transaction lifecycle and PCI-DSS boundaries.
• Direct payment-terminal / POS integration experience.
• Experience with cash automation and recyclers (Vynamic Cash or similar).
• End-of-day and reconciliation tooling experience.
• Regional acquiring experience (LatAm, EU, Middle East) and multi-currency payments.
• Loyalty, stored-value, gift, or wallet (Apple Pay / Google Pay) integration experience.
• Vendor certification experience with acquirers and processors; 3-D Secure / SCA, fraud/risk tooling.

Skills

• Extensive knowledge of Java and Spring framework.
• Strong OOP and distributed-systems design skills.
• Hands-on experience with serial and USB communication protocols.
• Experience with direct payment-terminal / POS integration.
• Understanding of the card transaction lifecycle and PCI-DSS boundaries.
• Experience with cash automation and recyclers.
• Regional acquiring experience and multi-currency payments.
• Vendor certification experience with acquirers and processors.

Benefits

The benefits package includes:

• Salary range: $150,000 - $185,000 DOE
• All full-time, regular employees and their dependents are eligible for medical, dental, vision, and FSA benefits.
• Additional health benefits include Healthcare and Dependent Care reimbursement programs, Employee Assistance Program (“EAP”), and Optum Care 24-hour confidential medical counseling services.
• Holidays: The company observes ten (10) paid holidays per calendar year.
• Paid Time Off (PTO): Full-time, regular employees earn 15 days of PTO in the first 12-months of continuous service, and 22 days in subsequent years. Eligible part-time employees earn pro-rated PTO.
• Retirement: Effective with your employment start date, you will be eligible to participate in the 401(k) Plan.
• Education, Learning & Development: We offer college tuition and education assistance programs; Udemy Learning courses; and ongoing learning and development opportunities.