(Senior) Fullstack Engineer - Freelance

the company is a trusted partner in digital commerce. The company helps leading brands modernize B2B solutions, marketplaces, and retail ecosystems. Since 2008, it has empowered businesses with cutting-edge technology, AI-powered personalization, and world-class engineering and design teams. A certified B Corporation®, the company is trusted by major brands including IKEA, VW, OLX, Delivery Hero, Żabka, Wolt, Careem, and Vinted.

How freelancing works at the company?

As a , you can choose what works well for you. You decide when, where, and how you work on projects and tasks. 

We match you with work that fits your skills. Plus, you have access to various opportunities across different industries and companies. That means you will not only gain more experience, but also develop various skills.

But there's more. the company freelancers can benefit from full-time collaboration and really be a part of the team.

So, are you ready to make an impact? Join the company, and let's build beautiful software together.

Currently we are looking for a Senior Fullstack Engineer who has successfully implemented Instagram Login before and can handle the entire process independently again.

Salary range: up to 160 PLN/h (on a B2B contract)

Engagement: fulltime

Working Hours: CET

Start date: 31.01.2026

Project duration: 2 months

Tasks & Responsibilities:

• Owning the 'App Review' Process: Managing the complete verification cycle with Meta (including creating required screencasts and writing scope justifications) to ensure the app is approved for Live access.

• Meta Ecosystem Configuration: Correctly setting up the application environment in the Meta for Developers console (identified by the client as the primary risk area).

• OAuth Strategy & Implementation: Implementing the 'Login with Instagram' flow to securely fetch specific influencer data points needed for profiling.

• Technical Advisory: Acting as the subject-matter expert to guide the client through Meta's strict policies and prevent application rejection.

Requirements

• fluency in Polish and English.

• OAuth 2.0.

• Instagram Graph API.

• Meta App Review experience.

Nice to have:

• Passport.js / NextAuth.js / OmniAuth (depending on stack).

• JWT (JSON Web Tokens).

• OpenID Connect (OIDC).

• Facebook Login Kit.

• GDPR compliance basics.

Benefits

In return, we offer:

• 100% remote, flexible work.

• Work with an experienced team of developers and continuous development of your hard and soft skills.

• Dev-friendly processes such as Continuous Integration, Continuous Delivery, Code Review and bug bashes.

• Long-term collaboration on challenging products (FinTech, B2B software, E-commerce and more).

Here's what you can expect from the recruitment process:

• First, you'll meet with one of our recruiters to get to know each other better.

• If everything goes well, you'll have the opportunity to meet with the client during an online interview.
  

Curious to learn more about working as a the company freelancer? All the information you need is here: .

Looking for a full-time job? Check out our and find out more about our open recruitment processes.

If you need any disability-related adaptation at any step of the recruitment process – simply let the recruiter know! We'd be happy to help.

Don't hesitate and apply right away.