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 evolve the payment-terminal platform behind our kiosks, including authorizing, capturing, voiding, refunding, reversing, settling, and reconciling transactions.
• Re-architect the platform into a modular, pluggable SDK so internal teams and external developers can build new integrations against a stable, versioned contract without forking the core.
• Implement new terminal integrations end-to-end, from byte-level protocols to the PayTerminal API, working directly with serial and USB transports.
• Partner with security/QSA teams on audits, driving architecture and design reviews, and mentoring engineers building integrations.

Requirements

• 6+ years of back-end engineering with strong Java expertise and solid OOP and distributed-systems design.
• Demonstrated experience designing extensible architectures and working with ServiceLoader, OSGi, or public SDKs.
• Hands-on low-level device and protocol experience, including serial and USB communication, and binary protocol implementation.
• Direct payment-terminal integration experience with Verifone, Ingenico, Adyen, Shift4, FreedomPay, SIX, Nepting, SiTef, Redsys, Worldpay, or similar systems.
• A 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.
• Experience with cash automation and recyclers, end-of-day and reconciliation tooling.
• Regional acquiring experience (LatAm, EU, Middle East) and multi-currency payments.
• Loyalty, stored-value, gift, or wallet integration experience.
• Vendor certification experience with acquirers and processors, including 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, and binary protocol implementation.
• Experience with direct payment-terminal 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

• Salary range: $150,000 - $185,000 DOE
• Health Benefits: Medical, dental, vision, FSA, healthcare and dependent care reimbursement programs, EAP, and Optum Care services.
• Holidays: Ten paid holidays per calendar year.
• Paid Time Off (PTO): 15 days in the first 12 months of continuous service, increasing to 22 days thereafter.
• Retirement: Eligibility for the 401(k) Plan.
• Education, Learning & Development: College tuition assistance, Udemy courses, and ongoing learning opportunities.

Pay

• $150,000 - $185,000 DOE

Schedule

• Full-time position based in San Diego, CA.