Full-Stack Developer – API Integrations & Analytics Web Platform

Hi! ????

We are a growing European media & e-commerce agency looking for a talented and reliable Full-Stack Developer to build a custom API-based web application with us.

This starts as a focused project but has strong potential to become a long-term development partnership with ongoing work and new features.

We are looking for someone who enjoys solving technical problems, thinks about architecture before coding, communicates openly, and takes responsibility for the quality of their work.

Full project details will be shared with shortlisted candidates.

What You Should Be Good At

The project involves connecting multiple external platforms, synchronizing and storing data, and displaying it in a multi-client web application.

Strong experience in several of the following areas is important:

• REST APIs & third-party API integrations
• OAuth 2.0 & token refresh
• PostgreSQL
• Multi-tenant architecture
• Background jobs / scheduled data synchronization
• Data normalization & historical data storage
• Secure authentication
• Role-based access control
• API rate limits, retries & error handling
• React / Next.js
• Node.js / NestJS or Python / FastAPI
• Git / GitHub
• Cloud deployment

Experience with APIs such as Shopify, Meta/Instagram, TikTok, Amazon, Pinterest or Google is a strong advantage.

Backend quality is more important than fancy design.

The frontend should initially be clean and functional. However, it must use reusable components and a well-structured frontend architecture, so that a professional Figma/UI design can easily be implemented later.

How We Want the Application to Work

At a high level, we are looking for an architecture similar to:

External APIs ? Background Synchronization ? Data Storage / Normalization ? PostgreSQL ? Backend ? Web Dashboard

We do not want external APIs to be queried every time a user opens the dashboard.

The application will eventually contain multiple clients, so proper and secure tenant separation is essential from the beginning.

The architecture should also make it easy to add additional API connectors later without rebuilding the entire system.

Technical Questions

Please answer the following questions briefly and in your own words.

Specific answers based on real experience are much more valuable to us than long textbook-style answers.

1. You need to collect analytics data from five different external APIs. Would you call all five APIs whenever a user opens the dashboard? If not, how would you structure the system?

2. A scheduled synchronization suddenly receives repeated HTTP 429 responses. What is happening and what would your application do?

3. An OAuth access token expires while a background synchronization is running. How would you handle this?

4. Twenty clients use the same application. How would you make sure Client A can never access Client B's data, even if someone manually modifies an API request?

5. API A calls a metric `spend`, API B calls it `cost`, and another API provides the value in cents. How would you design the data layer so the application can work with one consistent metric?

6. An API only provides the current follower count, but the application needs to show follower growth over the last 90 days. How would you solve this?

7. Tell us briefly about the most difficult third-party API integration you have personally built. What made it difficult and how did you solve it?

8. Which technology stack would you choose for this project and why?

We may discuss your answers during a short interview.

Paid Technical Trial – $65 Fixed Budget

Shortlisted candidates will be invited to complete the same small paid technical trial project.

Fixed trial payment: $65 USD

The trial is intentionally limited in scope and should take an experienced developer approximately 6–8 hours.

The trial will use a real e-commerce use case with restricted access to one of our own projects.

Trial Task

Build a small web-based analytics prototype that:

• Connects to one external API
• Retrieves selected real business data
• Stores the retrieved data in PostgreSQL
• Uses a basic synchronization process
• Displays approximately 3–5 KPIs
• Includes basic 7-day / 30-day filtering
• Includes a manual Sync Now function
• Uses a clean connector structure that could support additional APIs later
• Includes basic error handling
• Stores credentials securely

The required basic architecture is:

External API ? Synchronization ? PostgreSQL ? Backend ? Dashboard

The dashboard must read stored data from the database rather than calling the external platform every time the dashboard is opened.

Trial Deliverables

Please provide:

• Working prototype
• Source code in our Git repository
• Database schema / migrations
• Short README / setup instructions
• Brief explanation of your architecture
• Short section: “What I would improve for production”

Please do not spend unnecessary trial time on visual design.

A simple and clean interface is enough.

We are evaluating:

API integration ? architecture ? data accuracy ? security ? code quality ? problem solving

After submission, we may have a short call where we ask you to walk us through your implementation and explain some of your technical decisions.

We are completely comfortable with developers using modern AI-assisted development tools. What matters is that you understand, verify, can explain and take responsibility for the code you deliver.

Working Together After the Trial

If the trial is successful, we would like to continue development through clearly defined milestones.

Our preferred model is:

• Agreed hourly rate
• Clear scope for each milestone
• Estimated hours before starting
• Agreed maximum hour/budget range
• Review and approval before moving to the next milestone

We value transparency. If something takes longer than expected or an API creates an unexpected limitation, we want you to tell us early rather than silently spending additional hours.

There is significant potential for ongoing development work if the cooperation works well.

What We Value

Beyond technical skills, we appreciate someone who is:

• Reliable
• Honest
• Solution-oriented
• Organized
• Comfortable communicating technical limitations
• Able to work independently
• Interested in clean, maintainable code
• Open to feedback
• Interested in a long-term collaboration

If you think one of our technical ideas should be approached differently, tell us. We value developers who think with us rather than simply follow instructions.

How to Apply

Please include:

1. Your answers to the 8 technical questions
2. Your hourly rate in USD
3. Your weekly availability
4. Years of professional development experience
5. Your preferred technology stack
6. APIs you have personally worked with
7. Relevant GitHub, portfolio or project examples
8. Confirmation that the $65 paid trial works for you

Please start your application with: API Dashboard so we know you have read the complete job description.

We are looking forward to meeting you and hopefully building something great together!