Role summary

We are hiring a Senior Software Engineer to join our clients embedded engineering team. You’ll build production systems across our payments orchestration platform and contribute to the agentic AI/ML layer that decides the optimal way to pay every invoice. You’ll also mentor our graduate engineer, holding the bar on code quality and supporting their growth.

Your first twelve months

• Months 1–3. Finish and stabilise the platform migration (supported by the previous outsourced partner), close out required compliance work, and take full ownership of deployment. Much of this is inherited work. It is not glamorous, but it is the foundation for everything after it.
• Months 4–6. Automated tests run on every commit and block a bad merge. Deploys go through a pipeline, not by hand, and can be rolled back. A non-production environment can be rebuilt from code. Supplier verification and KYB automation are live. The graduate is shipping reviewed work without you unblocking them daily.
• Months 7–12. The data foundation and the first working version of the decision engine. This is where the product becomes genuinely defensible, and you will have built it.

The practical detail

• Production support. We run live payment rails. You are part of a shared escalation roster and are the technical escalation point for customer-impacting incidents. It is not a heavy on-call load, but it is real.
• Regulated environment. You will complete AML/CTF training on joining and annually and follow our data handling and change control obligations. Appointment is subject to a national police check.
• Performance Reviewed at. 3 months, 6 months, then annually, against the outcomes set out above.

Responsibilities

• Software engineering: Design, build and deploy production software across Lessn’s payments orchestration platform, including integrations with card networks, banks, the acquirer and payout rails.
• Data and AI engineering: Contribute to the design and delivery of the AI/ML decision engine that optimises how every invoice is paid (cheapest, most points, longest float, best use of cash, early-payment discount), using real-time open banking data. No prior AI/ML experience is required, we will teach you.
• Accounting integrations: Build and maintain reconciliation integrations with Xero, MYOB and future ERP platforms.
• Engineering process: Introduce and champion repeatable, scalable engineering practices, including CI/CD, automated testing and infrastructure-as-code.
• Mentorship: Mentor our graduate engineer. Review their code, support their development, and hold the quality bar on what ships.
• Quality: You are a senior line of defence before work reaches production in a regulated fintech environment. If it is not right, it does not go.
• Roadmap input: Feed insights from delivery back into the product roadmap, across vertical integrations, accounting connectors, the Payday Super module, multi-currency payments and real-time reconciliation.

Required experience

• 5+ years hands-on software engineering experience, including production systems in a commercial environment.
• Strong command of Python, and experience with at least one strongly typed language (C#, Java, C++ or similar).
• Experience with cloud infrastructure (AWS, Azure or GCP), infrastructure-as-code and containerisation.
• Demonstrated ability to design and ship software independently, with minimal oversight.
• Comfortable operating in a small team with direct exposure to founders and rapid decision-making.

Preferred experience

• Experience in fintech, payments or another regulated industry.
• Exposure to AI/ML engineering and the data pipelines that feed it (not required, we will teach you).
• Startup or scaleup experience in a fast-paced technology business.
• Experience mentoring or leading junior engineers

Skills and tools can be learned. These cannot:

• Curiosity that drives you to build, experiment and learn without being asked.
• Commercial pragmatism that solves the customer’s problem, not the most interesting one.
• Judgment that lets you pick an approach and move without perfect information.
• Directness that speaks the truth without ego getting in the way.
• Genuine satisfaction from making someone else better, not just shipping your own code.