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Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md). --- # Senior Software Engineer - Back End - **Company:** Tillster, Inc. - **Location:** Las Vegas, NV, United States - **Experience:** Expert - **Salary:** $150,000.0 - $185,000.0 - **Contract:** Permanent contract - **Skills:** Java (Programming Language), Application Programming Interfaces (APIs), Software Debugging, Apache Maven, Packet Analyzer, Object-Oriented Software Development, PCI Data Security Standards, RS-232, Simple Object Access Protocol (SOAP), Management of Software Versions, Concurrency, State Machines, Backend, Integration Tests, Verifone, Osgi, ISO 8583, Webhooks, Google Pay - **Published:** July 4, 2026 - **Apply:** https://www.indeed.com/viewjob?jk=eb1973864afa146b ## About the Role * 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. Nice-to-haves * Cash automation and recyclers (Vynamic Cash or similar), end-of-day and reconciliation tooling. * Regional acquiring experience (LatAm, EU, Middle East) and multi-currency payments. * Loyalty, stored-value, gift, or wallet (Apple Pay / Google Pay) integration. * Vendor certification experience with acquirers and processors; 3-D Secure / SCA, fraud/risk tooling. ## Description We are looking for a Senior Engineer (bordering on Architect) to own and evolve the payment-terminal platform behind our kiosks: a layer of 40+ integrations spanning card-present terminals, semi-integrated and cloud processors, and cash automation. You will re-architect this into a modular, pluggable SDK so internal teams and external/third-party developers can build new integrations against a stable, versioned contract without forking the core, and you will stay hands-on, implementing new integrations down to the wire-level protocol. What You'll Do (architecture and ownership) * 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. What You'll Do (hands-on, low to high level) * 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. ## Related Videos - [Developing the Backend with Stefan Lingler, CTO at Shpock](https://www.wearedevelopers.com/videos/100360-developing-the-backend-with-stefan-lingler-cto-at-shpock) - [Migrating half a million users to a new payment service provider](https://www.wearedevelopers.com/videos/730-migrating-half-a-million-users-to-a-new-payment-service-provider) - [Meet Your New BFF: Backend to Frontend without the Duct Tape](https://www.wearedevelopers.com/videos/682-meet-your-new-bff-backend-to-frontend-without-the-duct-tape) - [Nest.js - TypeScript in the backend can also be clean](https://www.wearedevelopers.com/videos/1033-nest-js-typescript-in-the-backend-can-also-be-clean) - [APIs and Architecture for scaling omnichannel payments](https://www.wearedevelopers.com/videos/90-apis-and-architecture-for-scaling-omnichannel-payments) - [Fintech Rebellion: How Developers Are Disrupting the Future of Commerce](https://www.wearedevelopers.com/videos/596-fintech-rebellion-how-developers-are-disrupting-the-future-of-commerce) ## Related Articles - [Highest Paying Tech Companies in Europe](https://www.wearedevelopers.com/magazine/162-highest-paying-tech-companies-in-europe) - [Backend Developer Salary in Germany [2023]](https://www.wearedevelopers.com/magazine/196-backend-developer-salary-in-germany-2023) - [Highest Paying Tech Companies for Developers](https://www.wearedevelopers.com/magazine/220-highest-paying-tech-companies-for-developers) - [Frontend Developer Salary in Germany [2023]](https://www.wearedevelopers.com/magazine/195-frontend-developer-salary-in-germany-2023) - [Software Developer Salary in Germany [2023]](https://www.wearedevelopers.com/magazine/194-software-developer-salary-in-germany-2023) - [Fullstack developer salary in Germany [2023]](https://www.wearedevelopers.com/magazine/197-fullstack-developer-salary-in-germany-2023)