Senior Software Engineer (Fullstack)

Atlas Systems; São Paulo; On-site; BRL 180,000 - 300,000; Full time

Benefits offered by this job

Stock options

Benefits matched in cash

Paid time off under PJ contract

Direct access to founders

Job summary

Atlas Systems in São Paulo is seeking a Senior Full-stack Engineer to own frontend and backend features across the stack.

You will build React dashboards and backend services in Java/Kotlin with Spring, and work with PostgreSQL data. You’ll ship end-to-end, emphasize correctness, performance, and security, and collaborate with Product, Design, Operations and Account Management.

Strong communication in English and pragmatic ownership are essential in this fast-moving fintech-like environment.

Qualifications

• 6+ years building web products in production at senior level.
• Strong React (and TypeScript) experience on complex data-heavy apps.
• Solid backend experience on JVM (Java or Kotlin, ideally Spring) or path from another typed backend language.
• Relational databases, e.g., PostgreSQL or similar.
• Strong CS fundamentals: data structures, algorithmic complexity and API design.
• Product sense: focus on user experience and simplifying flows.
• Pragmatism: shipping simple solutions within timeboxes.
• Ownership: delivered features end-to-end in production.
• Clear, concise communication in English.

Responsibilities

• Frontend: build and evolve the web product in React — dashboards, workflows and tools for hotel finance and operations teams.
• Backend: design and build services and APIs in Kotlin/Java with Spring.
• Translate complex payment and reservation data into clear interfaces for non-technical users.

Skills

Six plus years

React

TypeScript

Java/Kotlin

Spring

PostgreSQL

CS fundamentals

English communication

Ownership

Tools

React

TypeScript

Java

Kotlin

Spring

PostgreSQL

Job description

Zatlas is the payments automation platform for hospitality. We sit between hotels, their OTA partners and their acquirers, and recover the revenue that falls through the cracks. We are hiring a Senior Full-stack Engineer in São Paulo to build the payment and integration systems that hotels rely on to collect their revenue.

Our stack

Backend: Kotlin and Java with Spring

Database: PostgreSQL

Cloud: AWS

Observability: Datadog

Frontend: React (fullstack experience is a plus, not required)

Tooling: AI-assisted development (e.g., Claude Code) is part of our daily workflow

Kotlin is not required: strong Java engineers pick it up fast.

Why this role, and why now

We sit between hotels, their OTA partners and their acquirers, and recover the revenue that otherwise disappears: virtual credit cards (VCCs) that never get charged, cancellation and no-show fees that go uncollected, and payment methods that turn out to be invalid. Hotel finance and operations teams use our platform to see what is being left on the table and act on it, so the UI has to be clear, fast and precise with money.

We are backed by Kaszek and Picus Capital, have grown 5x year over year, and are expanding globally. Engineering is a small, all-senior team where every person has outsized impact. You will be a senior individual contributor who owns features end to end — from the React interface to the backend services and data behind it.

What you will own

1. The product, end to end

• Frontend: build and evolve our web product in React — dashboards, workflows and tools for hotel finance and operations teams.
• Backend: design and build the services and APIs that power those features, in Kotlin/Java with Spring.
• Turn complex payment and reservation data into interfaces that non-technical users understand at a glance.

2. Correctness and quality

• Own correctness end to end: what the screen shows must match what happened in the money flow.
• Keep code quality, performance, security, accessibility and observability high, including ownership of what you ship in production.

3. Architecture, collaboration and team

• Take part in architecture decisions, choosing the simple solution first and adding complexity only when needed.
• Work with Product, Design, Operations and Account Management to understand the hotel's problem before writing code.
• Help shape frontend standards and mentor teammates as the team grows.

Who we are looking for

We hire senior engineers who ship pragmatically and own outcomes across the whole stack, not just one layer.

MUST HAVE

• 6+ years building web products in production, currently at a senior level.
• Strong, recent React (and TypeScript) experience on complex, data-heavy applications.
• Solid backend experience on the JVM (Java or Kotlin, ideally Spring) or a clear path from another typed backend language, plus relational databases (PostgreSQL or similar).
• Strong CS fundamentals: data structures, algorithmic complexity and API design.
• Product sense: you care how users experience what you build and can simplify complex flows.
• Pragmatism: you pick the simplest solution that works, avoid over-engineering, and ship within a timebox.
• Ownership: you have taken a feature or product from zero to production and been accountable for it.
• Clear, concise communication, in writing and in conversation, including disagreeing with a real argument. Advanced or fluent English.

NICE TO HAVE

• Payments, fintech, B2B SaaS or high-scale platforms (e.g., Mercado Livre / Mercado Pago, Nubank, Stone, PagBank, PicPay, iFood).
• Data visualization and dashboards.
• Growth inside the same company (promotions, broader scope) and tenure that shows commitment.
• Startups or tech-driven companies where you built before you scaled.
• Intermediate Spanish — many of our clients are in Mexico.

PROBABLY NOT FOR YOU IF

• You want to stay in one layer of the stack — here you own features from the UI to the money flow.
• You prefer designing for every future case over shipping the simple solution within a timebox.
• You would rather hand code off than own it in production.

How we work

We work hard and keep it sustainable: focused days, rare weekends, and 2-month OKR cycles that make priorities and impact visible. The engineering team is flat and all-senior, with direct access to the founders, and works closely with Product, Design, Operations and Account Management. AI-assisted development is part of how we build every day.

Our hiring process

1. People Interview
2. Technical Interview
3. Manager's Interview
4. Founder's Meeting
5. Reference Check

What we offer

• Stock options — real ownership in a company growing 5x year over year.
• Benefits matched in cash, Wellhub, and paid time off under the PJ contract.
• A flat, all-senior engineering team with direct access to the founders.
• Real problems at scale: millions of transactions across multiple acquirers and the largest hotel groups in LATAM.
• Visible impact from week one, and room to grow into technical leadership.