Senior Backend Engineer (Node.js)

About this role

A Senior Backend Engineer (Node.js) is sought by Tonic Technologies in Lagos. The role focuses on maintaining and improving the production backend that powers the customer and partner-facing products, including wallets, gift cards, virtual cards, bills, and KYC flows for Nigerian and Ghanaian users. The candidate will ensure production-ready delivery, monitoring, and reliability, working with a Node.js/TypeScript stack (Express or NestJS) and a Kubernetes/GitOps setup. The company operates as a fintech startup providing payment solutions and services to a broad user base. The position emphasises real-world reliability, performance under load, and robust integration with third-party APIs and webhooks. Fully remote while Nigeria-based, with benefits including HMO, annual leave, and learning budget.

What you would do

• Build and maintain production backend systems used by consumer apps, partner API users, and internal admin tools.
• Design and iterate APIs to be clean and stable for frontend and partner developers.
• Investigate performance issues and optimise queries and workflows under load.
• Handle webhook processing and ensure wallet balances and transactions remain accurate.
• Work with payments, wallet funding, withdrawals, KYC, and multi-currency amounts that reconcile precisely.
• Ensure deployments are production-ready with monitoring and observability in place.
• Collaborate with cross-functional teams and provide constructive feedback to stakeholders.
• Manage and secure data flows, including authentication, secrets, and audit trails.
• Operate within a containerised environment deployed via Kubernetes and Argo CD.

What they are asking for

• 6+ years of experience building backend systems in Node.js with TypeScript.
• Strong understanding of idempotency, retries, race conditions, and database transactions.
• Experience integrating third-party APIs and webhooks with expectations of failures and duplicates.
• Focus on post-deployment reliability: logs, alerts, metrics, and on-call readiness.
• Ability to explain technical trade-offs to non-technical stakeholders.
• Commitment to security and customer data protection including auth and audit trails.
• Comfort using AI tools to improve velocity while safeguarding data privacy.
• Bonus: fintech/payments experience, ledger/wallet systems, card issuing or stablecoins, public API design, Kubernetes with Argo, incident post-mortems.

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