Senior Backend Engineer (Node.js) at Tonic Technologies

Overview
Why we need you:

• Our users never see the backend, but they feel it. Many are on a mid-range Android, two bars of network, and a battery at 14%. They tap “Fund card” once, the network drops, and they tap it again. They’re selling a gift card while the rate moves, or paying a bill five minutes before the light goes.
• If an API double-charges, times out halfway through a withdrawal, or shows a balance that isn’t true, that’s real money and real stress for a real person. We need someone who takes that personally.

Responsibilities
What you’ll actually be doing:

• You’ll build and maintain the systems people already depend on, not a greenfield side project. One backend powers everything, and everything hits it:
• The consumer app on iOS, Android and web: wallet, gift cards, Virtual Dollar Cards, bills, gadgets, eSIM. Used by customers in Nigeria and Ghana.
• The partner / B2B side: merchants and developers on our Gift Card API, who expect clean docs, stable versions and responses that don’t change mood.
• The internal admin dashboard: the tools Operations use to help customers. Privileged, audited, and not a place for shortcuts.
• Some days that’s designing an API so clean the frontend team stops sending you “quick question” DMs. Some days it’s figuring out why one query takes 4 seconds under load and getting it under 200ms. Some days it’s tracing a webhook from a payment partner that arrived twice, late, and in the wrong order, and making sure the wallet still tells the truth.
• You’ll own flows where mistakes cost money: payments, wallet funding, withdrawals, KYC, rates, card funding with Naira and stablecoins, and ₦, $ and ₵ amounts that must reconcile to the last kobo.
• Our services are containerised and ship to our Kubernetes cluster through Argo CD. You don’t need to be a platform engineer. You do need to be comfortable that “done” means deployed, monitored and behaving in production, not just merged.

The stack you’ll walk into:

• Node.js with TypeScript, plus a JavaScript codebase that already serves customers and needs your care. framework: Express / NestJS
• [Confirm database(s), e.g. PostgreSQL / MongoDB] and [confirm cache/queue, e.g. Redis, RabbitMQ / BullMQ]. You know when to index, when to queue, and when to wrap it in a transaction.
• REST APIs consumed by our web, mobile, partner and admin apps. Webhooks from payment, banking and card partners.
• Yarn, ESLint, Prettier, Husky, conventional commits. GitHub pull requests with a real review.
• Docker. GitOps (Argo CD) for what actually reaches production. Sentry for when things go bump.

Requirements
You’ll probably do well here if:

• You’ve spent [6+] years building backend systems in Node.js that real people use, and you write TypeScript without fighting it.
• You understand idempotency, retries, race conditions and database transactions, and you’ve used them for real, not just in an interview.
• You’ve integrated third-party APIs and webhooks, and you assume they will fail, duplicate, or time out at the worst moment.
• You care about what happens after the code ships: logs, alerts, metrics, and whether the 2am page is yours to fix.
• You can explain a technical trade-off to a PM without making them feel small, and you’ll ask “but what happens if the partner never responds?” when a ticket doesn’t say.
• You treat security and customer data as your job: auth, access control, secrets, audit trails.
• You use AI tools (Cursor, Copilot, Claude, ChatGPT, whatever works) to move faster, and you still read what they give you. You do not paste customer data (PII) or secrets into a model.

Bonus points if:

• You’ve worked in fintech or payments.
• You’ve built a ledger or wallet system with double-entry bookkeeping.
• You’ve worked with card issuing, virtual accounts or stablecoin rails.
• You’ve designed a public API that other developers actually enjoyed using.
• You’ve read a Kubernetes manifest or an Argo rollout without panic.
• You’ve handled a production incident and written the post-mortem. None of these are dealbreakers. They just make us smile.

This probably isn’t for you if:

• You think “it works on my machine” is a deployment strategy. Or you’d rather not think about what happens when a request runs twice. Or you only want to build new services and refuse to touch the code that already moves customers’ money. Or logs, tests and monitoring feel like someone else’s problem. No shade. Just not the fit.

What’s in it for you

• Fully remote, Nigeria-based. Your commute is from bed to desk (or bed to bed, we don’t judge).
• HMO. Annual leave. Work equipment and a learning budget.
• Your systems powering transactions for over a million users, plus the Operations team who rely on your APIs to help them.
• Teammates who will actually notice when you do something great.