API Developer

Job Title: API Developer
Location: London - 2 days per week in the office
Salary/Rate: Up to £450 Per Day (Inside IR35)
Start Date: 17/11/2025
Job Type: Contract (6 months)

Role Overview:

We have an exciting opportunity for a skilled API Developer to join an established technology team on a six-month contract. The successful candidate will be responsible for designing, building, and maintaining integrations between internal systems and external platforms using APIs and webhooks.

This role involves setting up secure API connections between platforms, managing authentication and data exchange, and configuring webhooks so systems automatically receive and process updates when specific events occur. For example, in a payment integration this could involve building the API connection to process transactions and setting up webhooks to notify the system when payments succeed, fail, or are refunded.

Key Responsibilities:

• Design, implement, and maintain API integrations between internal systems and third-party platforms.
• Configure and manage webhooks to enable Real Time updates and event-driven workflows.
• Ensure secure data exchange through proper authentication, encryption, and access management.
• Test, monitor, and troubleshoot integrations to maintain reliability and performance.
• Develop error-handling, retry, and logging mechanisms to safeguard data integrity.
• Collaborate with development, product, and operations teams to translate business needs into technical integration solutions.
• Maintain up-to-date documentation for integration workflows, endpoints, and system dependencies.
• Stay informed on best practices for API and webhook design, including scalability and security considerations.

Required Skills/Experience:

• Strong experience with RESTful APIs, webhooks, and related integration patterns.
• Proficiency with API authentication protocols (OAuth 2.0, API keys, JWT, etc.).
• Hands-on experience integrating third-party services such as Stripe, Salesforce, Adobe, or similar SaaS platforms.
• Solid programming or Scripting skills (eg Python, JavaScript, Node.js) for building and testing integrations.

If you are interested in this opportunity, please apply now with your updated CV in Microsoft Word/PDF format.

Disclaimer
Notwithstanding any guidelines given to level of experience sought, we will consider candidates from outside this range if they can demonstrate the necessary competencies.

Square One is acting as both an employment agency and an employment business, and is an equal opportunities recruitment business. Square One embraces diversity and will treat everyone equally. Please see our website for our full diversity statement.