Sr./Staff JavaScript Developer - Web SDK (Brazil/Canada/UK/Poland/India)

Oscilar; Brasil; Remote; BRL 250,000 - 380,000; Full time

Benefits offered by this job

Remote-first culture

Equity packages

401k

Health insurance

Unlimited PTO

Job summary

Oscilar is seeking a Staff JavaScript Developer to design, build, and optimize our Web SDK for device fingerprinting, identity verification, and behavior analytics. This role emphasizes SDKs over UI, requiring deep platform knowledge and collaboration across teams to deliver secure, scalable solutions.

You will lead design and performance optimization of the Web SDK, using JavaScript, TypeScript, and modern web tech, while mentoring engineers and aligning with privacy and security best practices.

Qualifications

• Bachelor’s degree or equivalent in CS/Software Eng
• 8+ years in web development, 3+ years building SDKs
• Proven open-source contributions or GitHub portfolio

Responsibilities

• Lead the development of a high-performance Web SDK for browser/device data
• Design algorithms for unique device fingerprints and behavior insights
• Maintain CI/CD with cross-browser testing and releases
• Optimize SDK performance for minimal resource usage
• Mentor junior engineers and conduct code reviews
• Collaborate with product/design/QA to meet high standards
• Ensure data privacy and security in SDK design

Skills

JavaScript (ES6+)

TypeScript

REST APIs

Git

Web SDKs

Browser APIs

Security Principles

Cross-browser Compatibility

Server-side Familiarity

Build Tools

Education

Bachelor’s degree in Computer Science or related

Tools

Webpack

Babel

Rollup

Job description

Shape the future of trust in the age of AI
At Oscilar, we're building the most advanced AI Risk Decisioning™ Platform. Banks, fintechs, and digitally native organizations rely on us to manage their fraud, credit, and compliance risk with the power of AI. If you're passionate about solving complex problems and making the internet safer for everyone, this is your place.

Why join us:

• Mission-driven teams: Work alongside industry veterans from Meta, Uber, Citi, and Confluent, all united by a shared goal to make the digital world safer.

• Ownership and impact: We believe in extreme ownership. You'll be empowered to take responsibility, move fast, and make decisions that drive our mission forward.

• Innovate at the cutting edge: Your work will shape how modern finance detects fraud and manages risk.

Job Description

We are seeking a highly skilled Staff JavaScript Developer to design, build, and optimize our Web SDK. This SDK will be at the core of our solutions for device fingerprinting, identity verification, and behavior analytics, enabling our customers to stay ahead in the ever-evolving fraud prevention landscape. This is not a UI or App development role, this is building SDKs for detecting fraud by analyzing device and behavioral properties. This requires deep understanding of the platform internals.

As a Staff Developer, you will lead the design, development, and performance optimization of our Web SDK, leveraging your deep expertise in JavaScript, TypeScript, and modern web technologies. You will collaborate across teams to deliver a secure, scalable, and developer-friendly SDK.

Responsibilities

• Lead the development and maintenance of a high-performance Web SDK for collecting and analyzing browser and device-related data.

• Design and implement algorithms to create unique device fingerprints and capture behavior-based insights (e.g., gestures, keyboard, and mouse interactions).

• Build and maintain a robust CI/CD pipeline with automated cross-browser testing and release cycles.

• Continuously optimize SDK performance to minimize resource usage and ensure a seamless user experience.

• Stay updated on emerging web technologies, security practices, and industry trends to enhance SDK capabilities.

• Develop clean, maintainable, and well-documented code aligned with the best coding practices.

• Conduct thorough code reviews and mentor junior engineers on best practices.

• Collaborate with cross-functional teams—including product managers, designers, and QA engineers—to meet high-quality standards and customer requirements.

• Ensure data privacy and security principles are embedded in the SDK’s design and implementation.

• Drive innovation in browser-based solutions for risk, fraud detection, and device analytics.

Technical Skills

• Proficiency: JavaScript (ES6+), TypeScript, REST APIs, Git, and version control tools.

• Web SDK Expertise: Extensive experience designing and maintaining Web SDKs or libraries with a focus on data collection, tracking, or analytics.

• Browser APIs: Deep understanding of browser environments, APIs, and efficient handling of browser-related data.

• Security Principles: Strong knowledge of data privacy, encryption, hashing, and obfuscation techniques.

• Cross-browser Compatibility: Experience in building solutions that work seamlessly across various browsers and devices.

• Server-side Familiarity: Understanding of server-side technologies and RESTful APIs for data retrieval and storage.

• Build Tools: Proficiency in modern build tools and frameworks like Webpack, Babel, or Rollup.

Soft Skills

• Excellent problem-solving abilities, with attention to detail and a focus on delivering high-quality solutions.

• Strong communication and collaboration skills to work effectively in cross-functional teams.

• Ability to mentor and provide constructive feedback to junior developers.

Education & Experience

• Bachelor’s degree in computer science, Software Engineering, or a related field (or equivalent experience).

• 8+ years of experience in web development, with at least 3 years focused on building and maintaining SDKs.

• Proven track record of contributing to open-source projects or showcasing relevant work on platforms like GitHub.

Preferred Qualifications

• Experience with AI-driven analytics, risk systems, or fraud prevention technologies.

• Familiarity with JavaScript SDKs, gestures, and interaction data processing.

• Prior experience in a high-scale, distributed environment.

Benefits

• Compensation: Competitive salary and equity packages, including a 401k

• Flexibility: Remote-first culture — work from anywhere

• Health: 100% Employer covered comprehensive health, dental, and vision insurance with a top tier plan for you and your dependents (US)

• Balance: Unlimited PTO policy

• Technical: AI First company; both Co-Founders are engineers at heart; and over 50% of the company is Engineering and Product

• Culture: Family-Friendly environment; Regular team events and offsites

• Development: Unparalleled learning and professional development opportunities

• Impact: Making the internet safer by protecting online transactions

If you are passionate about creating impactful web SDKs and enjoy solving complex challenges in risk and fraud prevention, we’d love to hear from you.