Senior Software Engineer - Design Systems

Mercury

Get hot jobs first on Telegram

New positions appear faster in our channel

Location: Canada, United States
Job Type: full-time
Work Format: 🌍 Remote
Salary: $200,700 - $250,900
Posted: November 7, 2026

Job Description

San Francisco, CA, New York, NY, Portland, OR, or Remote within Canada or United States

"We may say most aptly that the Analytical Engine weaves algebraic patterns just as the Jacquard loom weaves flowers and leaves."

— Ada Lovelace, 1843

What Lovelace saw in the loom was the pattern — flowers and leaves, repeated faithfully, each one begun by a hand that chose it. Mercury is built from patterns too. Every component, every interaction our customers come to trust, starts with someone deciding how it should go, and making it good enough to be used again and again. Tending those patterns, and giving everyone at Mercury the means to weave with them, is the work of our Design System team, and the north star of this role.

As a Senior Frontend Engineer on the Design Systems team, you will build and care for those patterns: the components and foundations that everything else at Mercury is built on. Done well, a single decision here makes every product team faster.

The ground under that work is shifting, though. Software is being built in new ways, and AI is increasingly part of how design systems are made and used. We are looking for someone who is fluent at that intersection: deeply versed in design systems, and equally as serious about what it takes to build a system that holds up at the leading edge of AI.

As part of this role, you will:

Build and maintain the components, patterns, and foundations (tokens, type, color, layout) that Mercury's product is woven from, holding a high bar for accessibility, performance, and pixel-level craft.
Lead projects that ship new UI patterns to solve real pain points for product teams, helping them build better experiences faster.
Develop a design system that's as ready for AI as it is for people, applying the technology to create leveraged outcomes.
Invest in the design system's prototyping experience, shaping the next iteration of how our design function rapidly prototypes, iterates on the product, and explores new concepts.
Raise the craft and AI fluency of the people around you, through mentorship and clear best practices.

The ideal candidate for the role:

We're looking for someone who cares about the foundational work that lets other people do their best work, and who's eager to help define what a design system means in a world where agents build alongside us. A successful candidate will likely have:

7+ years of frontend development, with deep experience in React, TypeScript, and modern web technologies.
Experience building or maintaining a design system or shared component library.
A thorough command of modern frontend tooling: build systems, CI/CD, and testing.
High agency, and comfort creating clarity in ambiguous spaces. You take ownership and move without waiting for a defined path.
First-principles systems thinking that stays oriented to outcomes. You make clear decisions that drive toward results instead of getting stuck in open questions.
Strong product taste, and an instinct for leverage: the change that makes many teams better, not the one component polished in isolation.
Hands-on fluency at the intersection of AI and software development: a real command of how emerging AI paradigms are changing the way software gets built, and the ability to turn that into practical leverage, both for the design system itself and for the people who build on it.

If this role interests you, we invite you to explore our public demo at demo.mercury.com.

*Mercury is a fintech company, not an FDIC-insured bank. Banking services provided through Choice Financial Group and Column N.A., Members FDIC.

Mercury values diversity & belonging and is proud to be an Equal Employment Opportunity employer. All individuals seeking employment at Mercury are considered without regard to race, color, religion, national origin, age, sex, marital status, ancestry, physical or mental disability, veteran status, gender identity, sexual orientation, or any other legally protected characteristic. We are committed to providing reasonable accommodations throughout the recruitment process for applicants with disabilities or special needs. If you need assistance, or an accommodation, please let your recruiter know once you are contacted about a role.

#LI-MC1

Total Rewards
The total rewards package at Mercury includes base salary, equity (stock options/RSUs), and benefits.

Our salary and equity ranges are highly competitive within the SaaS and fintech industry and are updated regularly using the most reliable compensation survey data for our industry. New hire offers are made based on a candidate’s experience, expertise, geographic location, and internal pay equity relative to peers.

Our target new hire base salary ranges for this role are the following:

US employees (any location):

$200,700 - $250,900 USD

Canadian employees (any location):

$189,700 - $237,100 CAD

🎯 Who is this job for?

Level: Senior frontend engineer with 7+ years of experience, ideally specializing in design systems and shared component libraries.

Required skills: Deep expertise in React, TypeScript, modern web technologies, accessibility, performance, frontend tooling, CI/CD, testing, and practical AI-assisted software development.

Relevant tasks: Building and maintaining reusable components, tokens, and patterns; leading design-system projects; improving prototyping workflows; solving ambiguous product problems; and mentoring teams on frontend craft and AI best practices.

💬 Potential Interview Questions

How would you architect a scalable React and TypeScript component library for use across multiple product teams?

I would establish clear component APIs, composable primitives, design tokens, accessibility requirements, and versioning policies. I would also provide strong documentation, examples, automated tests, and a release process that supports adoption without blocking product teams.

How would you design and implement a token system for color, typography, spacing, and layout?

I would define semantic tokens separately from primitive values so themes and product contexts can evolve without changing component code. Tokens should be consumed consistently across CSS, React, design tools, and documentation, with validation to prevent invalid or inaccessible combinations.

How do you ensure shared components meet accessibility requirements?

I use semantic HTML, correct keyboard behavior, visible focus states, accessible names, appropriate ARIA only when necessary, and support for screen readers and reduced motion. I would combine automated checks such as axe with keyboard testing and manual testing using assistive technologies.

How would you handle breaking changes in a design system used by many teams?

I would use semantic versioning, deprecation periods, migration documentation, codemods where practical, and clear release communication. Before making a breaking change, I would measure usage and provide an incremental migration path that minimizes disruption.

What testing strategy would you use for a production design system?

I would combine unit and interaction tests, accessibility checks, visual regression testing, and integration tests in representative applications. Critical components should also be tested across supported browsers, themes, responsive states, and failure conditions.

How would you improve the performance of a React component library?

I would measure first using browser profiling, bundle analysis, and real-user metrics. Improvements might include tree-shakeable exports, reducing unnecessary renders, avoiding expensive effects, lazy-loading optional functionality, and keeping component dependencies lightweight.

How would you design a component API that is flexible without becoming difficult to use?

I would optimize for the most common use cases with sensible defaults and expose composable escape hatches for advanced scenarios. I would avoid excessive configuration props, use consistent patterns across components, and validate the API through real product use rather than abstract completeness.

What CI/CD practices are important for a shared design system?

CI should run type checks, linting, unit and integration tests, accessibility checks, visual regression tests, and package build verification. Releases should be automated where possible, with preview builds, changelog generation, artifact validation, and controlled publishing to prevent regressions.

How could AI provide practical leverage in a design system?

AI could help generate component documentation, suggest token or component usage, identify inconsistencies, accelerate prototypes, and assist with migrations or test generation. I would keep humans responsible for design decisions, accessibility, security, and review, while grounding AI outputs in the system’s actual APIs and rules.

How would you make a design system usable by AI agents that generate interfaces?

I would provide machine-readable component metadata, explicit prop schemas, usage constraints, semantic token definitions, accessible composition patterns, and high-quality examples. The system should expose predictable primitives and validation tools so agents can generate valid interfaces instead of merely plausible markup.

📋 Job Summary

Mercury is a fintech company seeking a Senior Software Engineer to shape the design system powering its customer experiences. You’ll build and maintain accessible, high-performance components, tokens, and UI foundations; lead scalable product initiatives; improve prototyping workflows; and apply AI to help teams build better software faster. The role uses React, TypeScript, modern frontend tooling, CI/CD, and testing and is available in San Francisco, New York, Portland, or remotely across the United States and Canada. Compensation is $200,700–$250,900 USD for U.S. employees or $189,700–$237,100 CAD for Canadian employees, plus equity and benefits—an excellent opportunity to define the future of design systems at the intersection of product craft and AI.