Senior Software Engineer

Opulent Mind; City Of London; Hybrid; GBP 70,000 - 90,000; Full time

Job summary

Opulent Mind is seeking a Senior Backend Engineer to join a dynamic fintech team in London. In this role, you will design and build core services that accurately manage money transactions amidst complex financial scenarios. The successful candidate will have experience in backend systems and a deep understanding of fintech.

As part of a small team, you will have real ownership and the opportunity to grow into a technical leadership role. A background in payments or trading is preferred, allowing you to contribute significantly to the platform’s evolution.

Qualifications

• 5+ years shipping production backend systems.
• Experience in fintech, payments, banking, or trading preferred.
• Ability to design clean and simple solutions.

Responsibilities

• Design and ship core services for money transactions.
• Apply allocation rules and reconciliation logic.
• Make engineering decisions on simplicity and testability.
• Define integration of AI agents into the platform.

Skills

Production backend systems experience

Understanding of fintech and payments

Clean design solutions

Autonomy in ambiguous situations

Tools

TypeScript

Vue

TailwindUI

Job description

Build the engine room of a payments platform that actually understands money.

Most payments companies are wrappers. Money goes in, money comes out, and nobody can tell you why a particular merchant got paid the amount they did, against which rule, on which day.

Our client can. That is the whole product.

We're partnering on a search for a well funded London fintech orchestrating the messy middle of payments, pay-ins via cards, Direct Debit and open banking, explicit allocation between multiple parties, payouts that survive late failures, disputes and chargebacks weeks after the fact. The platform is live, first customers are onboarded, and there is a clear runway to transaction volumes in the hundreds of millions of pounds.

A second funding round closed earlier this year. The core is built. Now the team is shaping what comes next.

The problem you'd be working on

Payments look simple until you sit inside one. Cards settle on T+1 but can reverse at T+45. Direct Debit fails late. Open banking behaves like neither. On top of that sits a customer who needs to know, with certainty, who earned what and under which rule.

The team is building the system that holds all of that together and the embedded finance products that sit on top of it, so invoice native financing, regulated accounts, cards, phone as terminal. There is a real AI agent and decisioning layer underneath, grounded in transaction and behavioural data, not bolted on for a deck.

If correctness under uncertainty is the kind of problem that makes you lean forward, you'll like it here.

The role

You'd join a small team led by the CTO, working hands on across the backend platform. Real ownership, real scope, real production traffic. emote working with an office near Liverpool Street, the rest is yours.

This is a senior IC role with room to grow into technical leadership as the company scales. Expect to:

• Own end-to-end — Design and ship core services that move money correctly, even when the upstream world doesn't cooperate.
• Get the maths right — Apply allocation rules and reconciliation logic that hold up under audit and under load.
• Make sharp engineering decisions — Make pragmatic calls on simplicity, testability and blast radius and explain them clearly.
• Shape the next layer — Help define how AI agents plug into the platform without becoming a liability.

The stack

• Frontend — TypeScript, Vue, TailwindUI

You'll fit if

• You've spent 5+ years shipping production backend systems and can point at things you owned, not just things you touched.
• You've worked in fintech, payments, banking, trading, marketplaces or another domain where money or something just as unforgiving flows through your code. (Preferred, not required.)
• You design clean, simple solutions before clever ones. You know when a queue, an event log, or a boring SQL transaction is the right answer.
• You operate well with autonomy and ambiguity, and you reach out early when something looks wrong.
• You care about the person on the other end of the API, the checkout, or the pull request.

Where the business is

• Second funding round recently closed.
• Table stakes digital PSP built and live.
• Core platform running with real customers.
• Flagship marketplace and vertical SaaS onboarding with meaningful revenue impact.