Senior Software Engineer – Back End

Jobtailor; Austin (TX); On-site; USD 130,000 - 210,000; Full time

Job summary

Jobtailor in Austin seeks a senior backend engineer to own the payments domain end to end on our kiosk platform. You will architect a pluggable payment SDK and a unified terminal abstraction that works across integrated and cloud processors, while driving test harnesses and security patterns.

You will lead architecture discussions, mentor engineers, and ensure reliable money movement with strong adherence to PCI-DSS boundaries.

Qualifications

• 6+ years back-end engineering with strong Java (Spring) and distributed-systems design.
• Experience designing extensible plugin/SPI-based architectures (e.g. ServiceLoader, OSGi, Spring plugins).
• Hands-on low-level device and protocol experience: serial/USB and binary protocols (TLV/BCD).
• Direct payment-terminal / POS integration experience with major vendors.
• Solid grasp of card transaction lifecycle (auth, capture, void, refund, settlement) and PCI-DSS boundaries.
• Track record of technical leadership: driving design standards and mentoring engineers.

Responsibilities

• Own the payments domain end to end on the kiosk platform, including authorization, capture, void, refund, settlement, and reconciliation.
• Architect a pluggable payment SDK with plugin contract lifecycle and backward compatibility.
• Design a terminal abstraction across integrated, semi-integrated, and cloud processors with a single caller model.
• Build integration test/harness to validate new integrations before touching hardware.
• Define platform-wide patterns for money movement: idempotency, recovery, timeouts, concurrency, reconciliation.
• Lead architecture reviews, set integration layer direction, and mentor engineers.

Skills

Java

Spring

Distributed systems

SPI / plugin architecture

PCI-DSS / security

Low-level protocol TLV/BCD

Tools

Maven

Git

jssc

usb4java

REST/SOAP

ServiceLoader/OSGi

Job description

• 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

• 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.