I will integrate any third party API into your backend with tests

P
pscarvalho_dev
P
pscarvalho_dev
Paulo C
integrate any third party API into your backend with tests
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integrate any third party API into your backend with tests

About this gig

Most API integrations break in production for the same reasons: the token expires in a way nobody documented, the provider rate-limits you at the worst moment, or an error comes back in a shape your code never expected.


I have spent 18 years on that problem telecom systems for Ericsson and banking microservices for Itaú, where an integration failing quietly was not an option.


WHAT YOU GET

· Working integration with your existing backend

· Authentication done properly (API key, OAuth2, JWT whatever the provider uses)

· Retry with backoff, rate limit handling, and real error handling

· Tests that prove it works, not just a screenshot

· Clear notes on how to run and maintain it


WORKS WITH

Java and Spring Boot, Python, Node.js. Any REST or GraphQL provider payments, CRM, shipping, ERP, messaging, AI providers.


WHAT I NEED FROM YOU

The API documentation, credentials for a test account, and access to the repository.


You can see my work and background at paulosergiocarvalho.com.br


Message me before ordering with what you are integrating and I will tell you honestly which package fits or if it does not fit at all.

  • Expertise

    • Algorithms & Data structures
    • Debugging
    • Performance
    • Security
    • Databases

  • Programming language

    • Java

  • Frontend framework

    • Angular
    • Flutter
    • Next.js
    • React.js
    • Vue.js

  • Backend framework

    • Django
    • FastAPI
    • Node.js
    • Spring
    • Firebase

Get to know Paulo C

Paulo C

Backend and Integration Engineer

  • FromBrazil
  • Member sinceAug 2026
  • Avg. response time1 hour

  • Languages

    Portuguese, English
I have spent 18 years building backend systems that cannot afford to fail — telecom platforms for Ericsson, including three months on site in Sweden, and banking microservices for Itaú. Before that, five years on healthcare software for a Canadian company. What I do best is the unglamorous part: making a third-party API behave, untangling OAuth and rate limits, upgrading a Java project frozen on an old version, and finding the bug a team has been circling for weeks. Fixed scope, fixed price, tested code.

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