Contract Senior Full Stack Developer
Posted 2 days ago by WeDo
Negotiable
Outside
Undetermined
United Kingdom
Summary: The role of Senior Developer / Founding Engineer involves working with a pre-seed startup to enhance a mobile banking platform. Key responsibilities include integrating a Banking-as-a-Service provider, improving the existing architecture, and ensuring secure handling of financial data. The position requires a strong understanding of various technologies, particularly in a startup environment, and emphasizes security awareness in financial transactions. Immediate start is required for this contract opportunity outside IR35.
Key Responsibilities:
- Designing and building the ClearBank API integration
- Supporting virtual accounts, payment blocking, and transaction monitoring
- Handling webhooks and financial transaction data
- Extending the GraphQL schema and DynamoDB model
- Building new React Native mobile flows for spending controls, transaction history, and account setup
- Ensuring the platform handles PII and financial data securely and aligns with FCA / PSD2 expectations
- Evaluating and improving the current architecture
Key Skills:
- Experience with React, React Native, Node, TypeScript, and AWS
- Ability to build products from scratch in early-stage startups
- Comfortable working in small teams with high ownership
- Strong communication skills to articulate personal contributions and technical decisions
- Pragmatic approach to building without creating long-term technical debt
- Understanding of security and defensive programming in financial data handling
Salary (Rate): undetermined
City: undetermined
Country: United Kingdom
Working Arrangements: undetermined
IR35 Status: outside IR35
Seniority Level: undetermined
Industry: IT
Role: Senior Developer / Founding Engineer Contract Opportunity Outside IR35 UK or Europe Tech: React, React Native, Node, TypeScript, AWS Start date: Immediate Wedo is working with a pre-seed early stage start up who is building a mobile banking platform. The product already has a v1 application live with test users, which provides a solid starting point. However, there was limited handover, so part of this role will involve understanding the existing system and rationalising parts of the architecture as the product evolves. The immediate focus for the role is integrating a Banking-as-a-Service provider (likely ClearBank) and building the financial infrastructure required to support the product’s core mission. This includes:
- Designing and building the ClearBank API integration
- Supporting virtual accounts, payment blocking and transaction monitoring
- Handling webhooks and financial transaction data
- Extending the GraphQL schema and DynamoDB model
- Building new React Native mobile flows for spending controls, transaction history and account setup
- Ensuring the platform handles PII and financial data securely and aligns with FCA / PSD2 expectations
Current Architecture The current system spans several technologies including:
- React Native (Expo) mobile application
- TypeScript across both mobile and API layers
- Node.js / GraphQL (Apollo Server) backend
- Go-based AI chatbot service
- AWS infrastructure (Lambda, DynamoDB, API Gateway, Cognito, SSM)
- Terraform / Serverless Framework for infrastructure management
Part of the role will involve evaluating the current architecture and improving it where needed (for example moving parts of the API away from a purely serverless model to a more persistent database-backed approach). The strongest candidates will likely be engineers who:
- Have experience building products from scratch in early-stage startups
- Are comfortable working in small teams with high ownership
- Can clearly articulate what they personally built and why technical decisions were made
- Are pragmatic builders who can move quickly without creating long-term technical debt
Fintech or open banking experience is helpful but not essential, provided the engineer is comfortable integrating third-party APIs and understands the importance of security and defensive programming when handling financial data. Security Mindset Given the nature of the product, security awareness is critical — particularly around financial transactions, PII, token handling and protecting vulnerable users. To apply, connect with Jack Cole and send your CV to jack.cole@wedotech.uk. Equally, hit easy apply today.