About Mosaic
E-commerce in the US reached $1.3 trillion in 2025, accounting for 22% of all retail sales and growing at 10% a year. Sixty-five percent of consumers research products online before making any purchase, whether online or in store.
Independent retailers have not meaningfully participated in the e-commerce shift. The infrastructure built for online retail assumes a level of operational scale most independent stores do not have: warehouses, logistics, and digital marketing capabilities. A well-run boutique or specialty shop may have loyal customers and real inventory worth finding, but limited ability to reach people nearby who start their search online.
Mosaic is a local commerce marketplace built to counter this reality. Shoppers find nearby stores and browse real-time inventory through our consumer app. Retailers connect their existing catalog and payment systems and manage their storefront through our retailer app. Discovery, checkout, and order management run through one integrated platform. We are launching in Brooklyn NY.
The Role
We are looking for a Founding Engineer to own the technical execution that takes Mosaic from a nearly complete product to a live, operating marketplace and beyond.
The platform is substantially built. What stands between us and launch is the completion of our e-commerce connector, end-to-end validation of the payment and order flows, and the operational readiness to support our first stores and customers. After launch, the role expands into platform hardening, feature development, and scaling as we grow into new neighborhoods and markets.
You will work directly with our CTO on architecture and design decisions. You will own day-to-day engineering execution. You set the standards, make the calls, and ship the work.
What You Will Work On
• E-commerce connector: Complete and harden our Shopify integration, covering real-time inventory sync, the full order lifecycle, webhook reliability, and the edge cases that matter in a live marketplace. A detailed technical specification covers every scenario end-to-end. The primary work between now and launch.
• Marketplace payments: Validate and stress-test end-to-end payment flows built on Stripe Connect, including split payments, refunds, cancellations, and settlement. Correctness is not optional when real money is moving.
• Launch operations: Work alongside the founding team to onboard our first Brooklyn stores, respond to production issues in real time, and build the operational confidence to scale.
• Backend platform: Node.js, TypeScript, Express, and MongoDB Atlas. A large, well-documented REST API covering the full commerce and order lifecycle.
• Mobile apps: React Native and Expo across iOS and Android, covering neighborhood discovery and checkout on the consumer side and storefront management on the retailer side.
What We Are Looking For
• Strong full-stack engineer with deep Node.js and TypeScript experience and a real production track record. You have built, shipped, and operated systems.
• Payments experience in production. You understand what correctness looks like when real money is involved. Stripe experience is a strong plus; Stripe Connect experience even more so.
• Comfort with third-party API integrations: webhooks, idempotency, retry logic, and the operational discipline to keep data in sync under real-world conditions.
• React Native experience, or a strong React background with the appetite to own the mobile layer.
• Product-minded and decisive under ambiguity. You make sound tradeoff decisions without waiting to be told what to build.
• Genuine interest in the problem Mosaic is solving. These are real businesses, with real owners, operating on thin margins.
Nice to Have
• Shopify platform experience: Admin API, embedded app development, or webhook integrations.
• Marketplace or multi-vendor commerce experience.
• Cloud infrastructure experience: Azure, AWS, or GCP, CI/CD pipelines, and background job systems.
• Geospatial or location-based feature development.
The Commitment
We expect 20 or more hours of committed, focused work per week. In return, you get a real equity stake in what we build together, direct input into engineering decisions, and a genuine say in the team and culture we grow into.
Equity and Compensation
• Equity: 5% to 10% founding equity stake, commensurate with experience and contribution.
• Vesting: 6-month cliff from your start date, then monthly vesting over a 4-year total term.
• Salary: You will be a founding team member and equity holder. Compensation formalizes to a competitive full-time salary at our Series A.
Where We Are
Here is where we stand:
• Consumer app: 95% complete and tested
• Retailer app: 90% complete and tested
• E-commerce connector: In active development, with a comprehensive technical specification covering every scenario end-to-end
• 15 independent Brooklyn stores committed and ready to onboard at launch
• Angel investor engaged and committed to participate at launch
The Founding Team
Stefano, CEO and Co-Founder
Stefano began his career as a rocket scientist, developing satellite instruments for earth observation and deep space exploration. He then spent a decade leading product strategy for technology companies, working on multi-sided platform products including a KYC marketplace and a supply chain information-sharing network. He brings systems-level thinking and commercial strategy to a problem that requires both.
CTO and Co-Founder
Our CTO brings 20+ years of experience designing and delivering enterprise-scale technology systems across complex, high-availability environments. They designed and built the Mosaic platform from the ground up: the backend architecture, the marketplace payment infrastructure, and the mobile applications. They lead technical direction and work closely with the founding engineer on the decisions that shape the platform.
Tech Stack
Node.js | TypeScript | Express | MongoDB Atlas | Stripe Connect | React Native | Expo | Redux Toolkit | Azure | GitHub Actions | Shopify | iOS Dev | Android Dev | Stripe | Python | JavaScript | Rest APIs | GraphQL
How to Apply
Send your CV and a short note on why this resonates with you to [email protected]. GitHub or portfolio links are welcome.
Skills Required
- Deep Node.js and TypeScript experience with production track record
- Experience building and operating payment flows in production
- Familiarity with Stripe and Stripe Connect (split payments, refunds, settlements)
- Experience with third-party API integrations: webhooks, idempotency, retry logic, data sync
- Experience with React Native or strong React mobile app experience
- Experience with Express and MongoDB (Atlas) and REST/GraphQL APIs
- Proven ability to ship, operate, and troubleshoot production systems in real time
- Product-minded, decisive under ambiguity and comfortable making tradeoffs
- Ability to commit 20+ focused hours per week
- Shopify platform experience (Admin API, embedded apps, webhooks)
- Marketplace or multi-vendor commerce experience
- Cloud infrastructure and CI/CD experience (Azure/AWS/GCP, pipelines, background jobs)
- Interest in local commerce and working with small retailers
What We Do
Independent retailers have really struggled the last couple of years to ward off e-commerce giants: the infrastructure built for online retail was designed for a different scale: warehouses, logistics teams, dedicated marketing budgets. A boutique owner running the floor alone never had an equivalent. That is starting to change. Independent retailers are pushing back, and the scale advantage that once required massive infrastructure can now be delivered to a neighborhood store. Mosaic accelerates this shift. Shoppers find nearby independent stores and browse live inventory through our consumer app. Retailers connect their existing catalog and manage their storefront through our retailer app. Discovery, checkout, and order management run on one integrated platform, purpose-built for local, independent commerce. We are launching soon! Fifteen stores are committed and ready to go at launch, with an angel investor ready to participate too. The platform is nearly there: consumer app 95% complete, retailer app 90% complete. The hard problem is execution: syncing live inventory across retail systems, handling the full order lifecycle reliably, and making it simple enough for a store owner running the floor alone. That is what we have spent the past year solving. The founding team is a rocket scientist turned platform strategist and an enterprise systems architect with 20+ years building large-scale production systems. We are a small team at an early stage. The people who join now shape the product, the engineering, and the culture Mosaic grows into.
Why Work With Us
We want to help local businesses better compete against the e-commerce giants. We love the neighborhoods we live in, and care passionately about the social aspects local businesses, events, and people help to elevate
