Senior Software Engineer, Developer Platform

MoonPay

4d•Hybrid

About The Position

MoonPay is building a developer platform that enables partners to create native payment and crypto experiences within their own products. The platform turns MoonPay capabilities—including authentication, identity, KYC, quotes, payment methods, and purchasing—into reusable modules exposed through APIs, SDKs, embedded components, iframes, and web views. Its goal is to let partner developers integrate MoonPay without ongoing implementation support. This hands-on senior engineering role owns the developer-facing layer between MoonPay's payments infrastructure and partner products. The engineer will build the platform itself, rather than one-off customer integrations, working across browsers, mobile applications, and backend APIs to make complex financial workflows simple, predictable, and native. The work includes designing secure, stable APIs and SDKs; creating integration patterns for web and mobile; building reference applications, sandboxes, tooling, and practical documentation; and ensuring payment-critical flows remain reliable despite retries, duplicate events, delayed responses, or dependency failures. The role also covers versioning, compatibility, observability, adoption measurement, and ongoing platform evolution.

Requirements

Experience building APIs, SDKs, embedded components, or integration tooling used by third-party developers.
Strong understanding of browser or mobile behavior beneath the framework level, including sessions, storage, cross-origin communication, and embedded experiences.
Strong JavaScript and TypeScript fundamentals and experience building production client-side or SDK infrastructure.
Understanding of API and SDK design, including versioning, backwards compatibility, documentation, error design, and safe migrations.
Distributed systems experience, including handling duplicate, late, or out-of-order events and dependency failures.
Product judgment to turn complex platform capabilities into interfaces developers can understand and adopt.
Ownership of developer-facing software from design through launch, adoption, and ongoing production support.

Nice To Haves

Experience building payment APIs, checkout SDKs, embedded financial products, or payment-method integrations.
Experience building products similar to Stripe Elements, Stripe.js, Plaid Link, or Braintree client SDKs.
Experience with secure iframes, web views, postMessage, or cross-origin browser infrastructure.
Experience developing SDKs across web, iOS, or Android.
Experience building sandboxes, test environments, reference applications, or developer documentation.
Experience with webhooks, idempotency, transaction state machines, and payment orchestration.
Experience with authentication, identity, or KYC integrations.
Familiarity with cryptocurrency, wallets, or digital-asset products.
Familiarity with TypeScript, Node.js, React, GCP, PostgreSQL, Redis, and Kubernetes.

Responsibilities

Design and build APIs, SDKs, and embedded components for external developers.
Turn MoonPay authentication, identity, payment, and purchasing capabilities into reusable platform modules.
Develop secure browser and mobile integration patterns across iframes, web views, and native applications.
Create stable abstractions over payments, compliance, and crypto infrastructure.
Build reference applications, sandboxes, and tooling that help developers move from exploration to production.
Own the developer journey from obtaining credentials through completing a live transaction.
Design interfaces for sessions, authentication, quotes, payment methods, transaction state, and errors.
Handle browser and mobile concerns such as cross-origin communication, redirects, storage restrictions, and application lifecycle events.
Develop consistent behavior across web, iOS, and Android integrations.
Ensure integrations remain secure in products MoonPay does not control.
Design APIs and SDKs that are difficult to misuse and straightforward to debug.
Establish versioning, compatibility, and migration strategies.
Build documentation around real developer workflows.
Create useful errors, logs, and observability so partners can resolve issues without contacting MoonPay.
Reduce integration time and the need for direct engineering support.
Design payment-critical systems to handle retries, duplicate events, delayed responses, and failing dependencies.
Implement idempotency, state recovery, and graceful degradation across distributed payment flows.
Measure API and SDK adoption, integration success, reliability, and developer experience.
Safely evolve the platform as MoonPay adds products, payment methods, regions, and partners.

Benefits

Competitive salary package.
Equity package, with ownership for all employees.
Pay-for-performance equity bonus.
Moonshot award: 20 employees a year receive a $250,000 equity grant.
Pension with employer contributions from day one.
Employee referral program offering 10K in USDC.
Flexible Time Off.
Company-wide end-of-year Recharge Period.
Birthday leave.
Enhanced parental leave.
Hybrid working schedule, with the option to work fully remotely or from a nearby Moonbase.
Commuter benefits for public transport.
Private healthcare benefits.
Wellhub wellness membership.
Enterprise access to AI tools including Claude, ChatGPT, and Gemini.
Lunch credit for days worked in the office.
Home office setup allowance.
Remote working allowance for fully remote employees.
Monthly product budget and zero-fee crypto transactions.
$1,000 annual training budget.
High Potential Program with structured development, mentorship, and stretch opportunities.
Regular remote company offsites, including in-person sessions and hackathons.
Ireland Cycle to Work scheme.
UK EV Salary Sacrifice.