Back-end Engineer APIs

We're looking for a Back-end Engineer focused on API development to join our platform team. You'll design, build, and maintain the API layer that powers our C33 debt lending platform — connecting internal microservices, third-party financial providers, and client-facing applications through clean, reliable, and well-documented interfaces. If you care deeply about API design, developer experience, and building services that scale, this role is for you.

Key Responsibilities

• Design and develop RESTful APIs and microservices using TypeScript with NestJS
• Build and maintain integrations with third-party financial services (Stripe, GoCardless, banking APIs)
• Define and enforce API contracts using OpenAPI specifications
• Implement authentication, authorization, and security patterns (OAuth 2.0, JWT, Auth0)
• Build asynchronous communication patterns using Cloudflare Queues and WebSockets for real-time updates
• Optimize API performance, caching strategies, and database query patterns
• Develop and maintain integration tests, contract tests, and API monitoring
• Collaborate with front-end and mobile engineers to ensure seamless API consumption
• Contribute to system design decisions for multi-region deployment and high availability

Required Qualifications

• 5+ years of back-end development experience with a focus on API design and development
• Expert proficiency in TypeScript and Node.js
• Strong experience with NestJS or similar Node.js frameworks
• Deep understanding of RESTful API design principles and OpenAPI specifications
• Hands-on experience with both SQL (Clickhouse) and NoSQL (MongoDB) databases
• Solid knowledge of authentication/authorization patterns (OAuth 2.0, JWT)
• Experience with message queuing systems and asynchronous processing patterns
• Understanding of API versioning, rate limiting, and backward compatibility strategies
• Strong knowledge of security best practices for API development

Nice to Have

• Experience building financial or payment processing APIs
• Background in FinTech, lending, or alternative financing
• Familiarity with Cloudflare's ecosystem (Workers, R2, D1, Queues)
• Experience with GraphQL alongside REST
• Knowledge of financial compliance, KYC/AML processes, and regulatory requirements
• Experience with event sourcing and CQRS patterns
• Proficiency with Infrastructure as Code tools like Pulumi
• Experience with real-time data processing and WebSocket implementations

Tech Stack Highlights

• Backend: TypeScript, NestJS, Node.js
• Databases: Clickhouse, MongoDB, Redis
• Cloud Infrastructure: Cloudflare (Workers, Pages, R2, Queues), Azure, Kubernetes
• Payments & Banking: Stripe, GoCardless
• Monitoring: New Relic, Sentry
• Security: Auth0, JWT, OAuth 2.0

What We Offer

• A competitive and motivating income that recognizes and values your contributions.
• Opportunity to work on cutting-edge AI and FinTech challenges
• Flexible work schedule to promote work-life balance and accommodate your personal needs.
• Embrace a non-corporate and cozy work environment, where collaboration and creativity flourish.
• Modern tech stack with freedom to explore new technologies
• Direct impact on product direction and technical architecture
• Collaborative environment
• Regular team events and offsites
• Ample opportunities for professional growth and development, empowering you to reach new heights in your career.

Interview Process

1. Initial screening (20 minutes)
2. Technical test (90 minutes)
3. Cultural fit interview with leadership (45 minutes)
4. Reference checks and offer

How to Apply

Send your CV and a brief note about why you're excited to work in FinTech to [email protected]

Please include:

• Links to your GitHub/GitLab profile
• Examples of APIs or production systems you've built
• Your experience with our tech stack
• What interests you most about FinTech and AI

About Capital 33

Capital 33 is a next-generation merchant bank focused on two core services: capital raising and direct lending for mid-market and large enterprises. We support every stage of corporate growth—from day-to-day working-capital needs to multi-year investment programs—leveraging deep expertise in structured finance, syndicated loans, private debt, and project finance. We're building the future of FinTech by combining cutting-edge artificial intelligence with deep financial expertise to provide startups with the capital they need to grow.

Capital 33 is an equal opportunity employer committed to building a diverse and inclusive team. We welcome applications from all qualified candidates regardless of race, gender, age, religion, identity, or experience.