Software Engineer - Front

OpenKrill; United States; Hybrid; USD 101,000 - 146,000; Full time

Benefits offered by this job

Stock options

Unlimited PTO

Health insurance for family

Transit reimbursement

Hybrid work model

Paris office

Remote work allowance

39-hour workweek

Job summary

Ussunday, headquartered in Paris, seeks a Senior Software Engineer to deliver full-stack features in Kotlin and React, leveraging AI agents to accelerate development. You will own complex topics from architecture to reliability and contribute to scalable services handling high loads.

The role requires hands-on experience with Kotlin backend and React frontend, production deployments, and fluent FR/EN communication. The position offers a hybrid work model based in Paris with generous benefits.

Qualifications

• Proven full-stack development with Kotlin on backend and React.js on frontend.
• Experience deploying high-load services in production.
• Hands-on experience with AI agents or AI-assisted tooling.
• Ability to reason about architecture, reliability, and trade-offs.
• Strong business sense and prioritization skills.
• Fluency in French and English (spoken and written).

Responsibilities

• Design and deliver high-quality full-stack features from Kotlin backend services to React.js frontend applications.
• Write code using AI agents and help build an agentic software factory.
• Own complex topics related to software design, architecture, and service reliability.
• Design scalable production-ready solutions.
• Improve development practices and engineering efficiency through agentic AI.
• Make pragmatic technical decisions considering business impact, simplicity, and speed.
• Share standards and learnings to help the team grow.

Skills

Kotlin backend

React.js frontend

AI agents

System architecture

Production scale

Bilingual FR/EN

Job description

About Ussunday

About Ussunday is building the fastest, simplest way to pay in restaurants. With a quick scan of a QR code, diners can pay, tip, and leave in about 10 seconds. We believe great products should feel obvious, not complicated, and we focus relentlessly on keeping things simple while earning trust from restaurants and guests at every interaction. Today, sunday powers payments in thousands of restaurants across the US, UK, and France, helping operators turn tables faster, increase tips, and unlock valuable insights. We push ourselves to go beyond what’s expected, building with ownership, moving fast, and scaling with ambition as we tackle our biggest growth opportunity in the US.

About the Role

As a Senior Software Engineer, your goal will be to design and deliver high-impact full-stack features, from Kotlin backend development to React frontend experiences, while accelerating the way we build software through AI agents. You will report to Nicolas and join the Tech team. You will take ownership of complex technical challenges, make the right trade-offs between speed, simplicity, and robustness, and directly contribute to building services capable of handling high loads.

Key Responsibilities

• Design and deliver high-quality full-stack features, from Kotlin backend services to React.js frontend applications.
• Write code using AI agents and help build a true agentic software factory.
• Take ownership of complex topics related to software design, architecture, and service reliability.
• Design solutions capable of running in production at scale.
• Continuously improve development practices and Engineering team efficiency through agentic AI.
• Make pragmatic technical decisions, taking business impact, simplicity, and execution speed into account.
• Share your standards, learnings, and technical convictions to help the team grow.

About You

What we’re looking for:

• Several years of full-stack development experience, with strong hands‑on expertise in Kotlin on the backend and React.js on the frontend.
• Proven experience deploying and operating high-load services in production.
• Hands‑on experience writing code with AI agents or AI‑assisted development tools.
• The ability to reason about architecture, reliability, and technical trade‑offs.
• Strong business acumen: you understand the impact of your decisions and know how to prioritize what truly matters.
• Fluency in both French and English, spoken and written.

What will set you apart

• Strong ownership: you tackle problems head‑on rather than waiting for permission.
• An entrepreneurial mindset, strong adaptability, and a willingness to thrive in ambiguous environments.
• Independent thinking: you know how to reframe problems and find simple, original, evidence‑based solutions.
• A strong focus on impact, with the ability to make clear trade‑offs and apply the 80/20 principle.
• Positive energy, a collaborative mindset, and a desire to help the entire team succeed beyond your own scope.
• Intellectual curiosity, the ability to learn quickly, and a genuine desire to keep improving.

Compensation, Perks & Benefits

• A competitive package, depending on experience, plus stock options.
• Unlimited paid time off.
• Significant ownership and numerous opportunities for career growth.
• 100% employer‑paid health insurance coverage for you and your children.
• 50% reimbursement of your public transportation pass.
• Beautiful offices in the heart of Paris, in the Sentier district.
• A hybrid working model combining office presence and remote work.
• €50 per month towards remote‑working expenses.
• A 39‑hour working week under an executive employee status (statut cadre).

Interview Process

• Step 1 - HR Screen (30 mn)
• Step 2 - Hiring manager interview (30 mn)
• Step 3 - Technical interview
• Step 4 - Culture fit interview (30mn)
• Step 5 - Reference checks

Thank you for taking the time to apply, and looking forward to getting to know you!

sunday is an equal opportunity employer and does not discriminate and all qualified applicants will receive consideration for employment without regard to race, creed, color, sex, affectional or sexual orientation, gender identity or expression, gender, ethnicity, religion, national origin, ancestry, nationality, age, disability, marital status, veteran status, genetic information, or on any other basis prohibited by law (except where an attribute is a bona fide occupational qualification).