Senior / Staff Fullstack Software Engineer

Techifide; São Paulo; On-site; BRL 180,000 - 240,000; Full time

Job summary

Techifide is seeking a Senior or Staff Fullstack Engineer who owns features from browser to services. You will work on a modern React/TypeScript frontend with Python and Rust services, integrating AI agents and external APIs while ensuring a fast, intuitive user experience.

The role emphasizes end-to-end ownership, collaboration with ML engineers, and producing high-quality, well-tested code that scales in production.

Qualifications

• Proficient in React and TypeScript with strong front-end architecture.
• Experience integrating AI agents or AI services into production applications.
• Backend collaboration with Python and Rust services for business logic and data exchange.
• Understanding data journeys from browser to backend and streaming results.
• Ability to own features from concept to production across multiple tech stacks.

Responsibilities

• Own features from concept through production across React/TypeScript, Python and Rust.
• Build responsive, high-performance user experiences with React/TypeScript.
• Integrate AI agents and ML services into product workflows.
• Contribute to Python and Rust services responsible for business logic and data exchange.
• Design and evolve API contracts with frontend and backend engineers.
• Integrate third-party platforms and APIs with authentication and latency considerations.
• Work with streaming data to deliver reliable results to the browser.
• Analyze performance across the stack and optimize accordingly.
• Collaborate with product, design and ML teams to turn ideas into features.
• Write well-tested code and participate in code reviews.

Skills

React

TypeScript

Python

Rust

WebAssembly

AI integration

API design

Performance optimization

Tools

Git

CI/CD

Job description

We're looking for a Senior or Staff Fullstack Engineer who enjoys owning a feature all the way from the browser to the services behind it.

You'll work across a modern React and TypeScript application, Python and Rust services, external APIs, and an AI agent platform. The role has a strong front-end focus, but this isn't a position where you throw an API request over the wall and wait for someone else to deal with the rest.

You'll be expected to understand the complete journey of the data: how it reaches the application, how agents and services process it, how results are streamed back, and ultimately how those results become a fast and intuitive experience for the user.

You'll also work closely with machine learning engineers to turn sophisticated AI capabilities into practical product features people can actually use.

This is a hands-on engineering role for someone who likes difficult product problems, takes ownership and cares about the quality of what reaches production.

What you'll be doing

• Own features from concept through production across React/TypeScript, Python and Rust.
• Build responsive and high-performance user experiences using React and TypeScript, with particular attention to component architecture, state management and browser performance.
• Integrate AI agents and machine learning services into real product workflows, turning complex underlying capabilities into simple user experiences.
• Contribute to Python and Rust services responsible for business logic, data exchange, agent orchestration and communication with the client application.
• Design and evolve API contracts alongside platform and backend engineers, making sure services provide the data and behaviour the application needs.
• Integrate third-party platforms and APIs while accounting for authentication, rate limits, retries, latency and failures.
• Work with streaming and real-time data, ensuring results are delivered reliably and efficiently to the browser.
• Investigate performance across the entire application, from browser memory and rendering through API calls and backend services.
• Collaborate directly with product managers, designers, ML engineers and other software engineers to turn ideas into clearly defined features.
• Write maintainable, well-tested code, contribute to code reviews and improve areas of the codebase that need attention.

What we're looking for

You've already worked at Senior or Staff level building sophisticated web applications used in production.

You should have:

• Strong React and TypeScript experience, including complex component architecture, state management and performance optimisation.
• Experience working with WebAssembly in the browser, including integrating WASM modules with JavaScript or TypeScript and diagnosing performance issues across that boundary.
• Experience integrating LLMs, AI agents or similar AI services into production applications.
• An understanding of the realities of AI-powered applications, including streaming responses, tool calls, unpredictable latency, errors and partial results.
• Experience integrating external APIs and designing around authentication, rate limiting, retries and service failures.
• Strong debugging skills across the stack. You should be comfortable following a problem from the browser, through network requests and backend services, into infrastructure logs.
• Good knowledge of front-end architecture and patterns for building complex, stateful applications.
• Production experience with at least one of our backend languages: Python or Rust.
• Experience using AI-assisted development tools as part of your normal engineering workflow.
• The communication skills to work effectively across engineering, product, design and machine learning teams.

Most importantly, you should be comfortable joining an evolving product and codebase where not every problem has already been neatly defined.

Nice to have

Experience in any of these areas would be particularly useful:

• 2D or 3D graphics, CAD or geometry-heavy applications.
• WebGL, WebGPU or Three.js.
• AWS infrastructure and managed services.
• Production observability, including logging, tracing and monitoring.
• CI/CD and GitLab pipelines.
• Agile product development.

The kind of engineer who will enjoy this role

You probably won't enjoy this position if you want to work exclusively on isolated front-end tickets.

You probably will if you like understanding how the whole product works, are willing to move between React, APIs, backend services and AI systems, and enjoy taking responsibility for getting something from an idea to a polished feature in production.

The problems are technically challenging, the product is ambitious, and you'll have the opportunity to influence how both the application and its engineering architecture evolve.