Senior Backend Engineer – Fintech/Crypto Wallet Infra

As a Senior Backend Engineer at Eko Xchange, you take ownership of the backend systems, wallet infrastructure, blockchain integrations, and transaction-processing architecture for a custodial digital-asset exchange preparing for production launch. This is a hands-on role for someone who understands the technical and operational demands of building a custodial crypto product, not simply someone who has integrated a few blockchain APIs.

What you'll do

• Design, develop and maintain scalable, secure backend services and APIs.
• Build and maintain services supporting user accounts, authentication, KYC, asset management, deposits, withdrawals, transfers, swaps and transaction histories.
• Develop reliable transaction-processing workflows, including transaction states, confirmations, retries, error handling, and reconciliation.
• Maintain clean, modular, documented and maintainable code.
• Implement and maintain custodial wallet infrastructure using secure wallet-as-a-service or key-management providers.
• Integrate blockchain networks, RPC endpoints, node providers and blockchain data services.
• Work with signing services, wallet creation, address derivation, transaction broadcasting and transaction monitoring.
• Implement deposit detection, balance updates, confirmation tracking, withdrawal processing and blockchain transaction reconciliation.
• Understand network-specific requirements, including UTXO-based networks such as Bitcoin and account-based networks such as Ethereum and Solana.
• Investigate and optimise RPC usage, API credit consumption, background jobs, polling, webhooks and event-driven monitoring.
• Implement gas sponsorship or transaction-relaying integrations where supported and appropriate.
• Apply secure coding practices, access controls, secrets management and appropriate signing policies.
• Build safeguards against duplicate transactions, replay attempts, unauthorised withdrawals and other common blockchain application risks.
• Implement logging, monitoring, alerting, audit trails, backups and recovery procedures.
• Identify vulnerabilities, performance bottlenecks and infrastructure risks before production deployment.
• Manage backend deployment environments, databases, server configurations and CI/CD processes.
• Monitor service availability, performance and infrastructure costs.
• Diagnose production incidents and implement sustainable fixes.
• Maintain deployment documentation and ensure the company can operate and maintain its infrastructure independently.
• Work closely with frontend developers, product management and QA.
• Provide clear API documentation, implementation notes and integration requirements.
• Break down work into measurable deliverables and communicate progress, blockers and technical dependencies promptly.
• Support QA, integration testing, release preparation and production deployment.
• Design, develop and maintain independent backend microservices.
• Manage service-to-service communication, API contracts, authentication and data exchange.
• Implement reliable inter-service communication, error handling, retries, timeouts and failure recovery.
• Manage service dependencies, database interactions, background workers and asynchronous processing.
• Diagnose issues across multiple services and ensure consistent data flow and transaction states.
• Optimise service performance, scalability, observability and infrastructure costs.
• Ensure services can be independently deployed, monitored, tested and maintained.

What you bring

• At least 5 years of professional backend engineering experience, with demonstrable senior-level ownership of production systems.
• Proven experience building and deploying a cryptocurrency exchange, custodial wallet platform, digital-asset application or comparable blockchain-based financial product.
• Experience taking a digital-asset product from development through testing, deployment and live production operation.
• Strong proficiency in at least one backend language and framework, such as Node.js/TypeScript, Python, Go or Java.
• Strong experience designing REST APIs and integrating third-party services.
• Practical experience with relational databases, preferably PostgreSQL, including schema design, query optimisation and transaction management.
• Hands-on experience with blockchain RPC providers, node infrastructure, webhooks, transaction monitoring and blockchain data retrieval.
• Understanding of wallet architecture, private-key security, transaction signing, address derivation and blockchain confirmation mechanisms.
• Experience with cloud infrastructure, Linux servers, Docker, CI/CD and production monitoring.
• Ability to troubleshoot complex technical issues independently and explain technical decisions clearly.
• Demonstrable hands-on experience designing, developing and maintaining microservices-based applications.
• At least 2 to 3 years of practical microservices experience, preferably within production environments.
• Strong understanding of distributed systems, service boundaries, inter-service communication, API gateways, asynchronous processing and failure handling.
• Experience troubleshooting production issues involving multiple interconnected services.
• Ability to assess an existing microservices architecture, identify unnecessary complexity and recommend practical improvements.

Nice to have

• Experience with Turnkey, Fireblocks, Privy or comparable wallet/key-management infrastructure.
• Experience with Ethereum and EVM-compatible networks, BNB Chain, Solana, Bitcoin and Tron.
• Bitcoin UTXO management, address indexing and transaction monitoring.
• Experience with RPC providers such as QuickNode, Alchemy, Tatum, Chainstack or equivalent.
• Gas sponsorship, relayers, paymasters and sponsored transactions.
• Crypto liquidity, exchange execution, deposit and withdrawal infrastructure.
• KYC/AML integrations and payment-provider integrations.
• High-volume background processing, queues, event-driven systems and distributed services.

About Eko Xchange

Eko Xchange is building a custodial digital-asset exchange that enables users to buy, sell, send, receive and swap digital assets through a secure and accessible platform.