Senior Software Engineer – Back End

Tillster

Senior Engineer responsible for back-end payment terminal architectures at Tillster. Leading integrations and re-architecting platforms for enhanced functionality within kiosk systems.

Posted 7/3/2026full-timeAustin • Texas • 🇺🇸 United StatesSenior💰 $150,000 - $185,000 per yearWebsite

Tech Stack

Tools & technologies

CloudJavaMavenSOAPSpring

About the role

Key responsibilities & impact

Own the payments domain end to end on the kiosk platform: authorize, capture, void, refund, reversal, settlement (EOD), and reconciliation.
Re-architect the platform into a pluggable payment SDK: design the plugin contract and lifecycle (discovery/registration, versioning and backward compatibility, capability negotiation, dependency isolation, per-integration configuration and secrets) on top of the existing PayTerminal SPI.
Design a terminal abstraction that cleanly spans integrated vs. semi-integrated vs. cloud/REST processors and cash devices, so callers code to one model regardless of transport or vendor.
Build the integration test and certification harness (extending the current mock-terminal approach) so a new or external integration can be validated, simulated, and regression-tested before it touches real hardware.
Set platform-wide patterns for correctness in money movement: idempotency, transaction recovery and reversal, timeouts, heartbeat/health, concurrency, and reconciliation, in a system where double-charges and dropped captures are unacceptable.
Design for PCI-DSS scope minimization: tokenization, P2PE, per-processor TLS/mTLS and certificate/key handling, so cardholder data stays out of in-scope services. Partner with security/QSA on audits.
Drive architecture and design reviews, set technical direction for the integration layer, and mentor engineers building integrations.
Implement new terminal integrations end to end, from byte-level protocol (framing, TLV/BMP/APDU, BCD/LLVAR, checksums, ACK/NAK state machines) up to the high-level PayTerminal API.
Work directly with serial (RS-232 / USB-serial via jssc) and USB (usb4java) transports: port handling, event-driven reads, reconnection, and timing.
Integrate high-level and cloud processor APIs (REST/SOAP, webhooks, semi-integrated terminal SDKs) with robust retry, polling, and reconciliation.
Debug live hardware: protocol traces, terminal logs, packet captures, and vendor certification cycles.

Requirements

What you’ll need

6+ years back-end engineering with strong Java (the platform is multi-module Maven/Java on Spring) and solid OOP and distributed-systems design.
Demonstrated experience designing extensible / plugin / SPI-based architectures (ServiceLoader, OSGi, Spring plugin models, or public SDKs consumed by other teams or third parties).
Hands-on low-level device and protocol experience: serial and/or USB communication and binary protocol implementation (TLV, BCD, bitmaps, length-prefixed fields, state machines). EMV, ISO 8583, ZVT, or OPI a strong plus.
Direct payment-terminal / POS integration experience (Verifone, Ingenico, Adyen, Shift4, FreedomPay, SIX, Nepting, SiTef, Redsys, Worldpay, or comparable), and a clear understanding of integrated vs. semi-integrated models.
Solid grasp of the card transaction lifecycle (auth, capture, void, refund, settlement, reversal) and PCI-DSS boundaries, tokenization, and TLS/mTLS in production.
Track record of technical leadership: leading designs, setting standards, and mentoring engineers.

Benefits

Comp & perks

Health Benefits: 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.

ATS Keywords

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Applicant Tracking System Keywords

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Hard Skills & Tools

Back-End EngineeringDistributed Systems DesignOOPProtocol ImplementationTransaction Lifecycle ManagementTokenizationSerial CommunicationUSB CommunicationIntegration TestingMaven

Soft Skills

MentoringTechnical DirectionCollaboration