Senior Mobile Platform Engineer (Wallet SDKs)

Circle (NYSE: CRCL) is one of the world's leading internet financial platform companies, building the foundation of a more open, global economy through digital assets, payment applications, and programmable blockchain infrastructure. Circle's platform includes the world's largest regulated stablecoin network anchored by USDC, Circle Payments Network for global money movement, and Arc, an enterprise-grade blockchain designed to become the Economic OS for the internet. Enterprises, financial institutions, and developers use Circle to power trusted, internet-scale financial innovation. Learn more at circle.com .
What you'll be part of:
Circle is committed to visibility and stability in everything we do. As we grow as an organization, we're expanding into some of the world's strongest jurisdictions. Speed and efficiency are motivators for our success and our employees live by our company values : High Integrity, Future Forward, Multistakeholder, Mindful, and Driven by Excellence. We have built a flexible work environment where new ideas are encouraged and everyone is a stakeholder.
What you'll be responsible for:
We are looking for a Mobile SDK Engineer to build, ship, and own Circle Wallet SDKs for iOS (Swift), Android (Kotlin), and React Native/Expo. You will deliver production-grade SDK capabilities end to end, from implementation and testing through packaging, releases, and developer documentation. You will drive cross-platform consistency by aligning shared behaviors and error handling, and by improving integration reliability for external developers. You will work closely with Product, Backend, Support, and Security to troubleshoot customer issues, review security-sensitive changes, and continuously raise the bar on quality, performance, and maintainability. This is a high-impact opportunity to shape how developers integrate Circle Wallet experiences across mobile ecosystems.
What you'll work on:

• Build, ship, and own Circle Wallet SDKs for iOS (Swift) , Android (Kotlin) , and React Native/Expo that help developers embed wallet creation, authentication, signing, and transaction flows into their apps.
• Primarily own more than one SDK area (e.g., iOS + RN bridge, Android + release/tooling) while contributing across the broader SDK ecosystem to deliver a consistent, developer-first experience.
• Help drive cross-SDK consistency by contributing to both mobile SDKs and server-side SDKs (e.g., TypeScript/Node.js, Python ), including shared behaviors, error models, and documentation.
• Design and evolve mobile SDK public APIs with strong API ergonomics, backwards compatibility, and predictable versioning.
• Own features end-to-end: requirements and API design, implementation, unit/integration testing, packaging and distribution, releases, changelogs, and developer documentation.
• Build and maintain security-sensitive components, including key management and secure storage using platform primitives (e.g., Android Keystore, iOS Keychain + Secure Enclave ), and partner with Security on threat modeling and reviews.
• Improve developer onboarding and integration success rate with clear docs, sample apps, integration guides, and developer tooling (including predictable releases and upgrade paths).
• Collaborate with Product, Backend, and Support teams to debug and resolve real customer issues, and continuously raise the bar on quality, reliability, and performance.
• Leverage AI-assisted development tools (for code, tests, and docs) to move quickly while keeping quality and security bars high.

What you'll bring to Circle:
Core Requirements:

• 4+ years of professional SDK / library development experience (mobile preferred).
• Proficiency with TypeScript and React Native/Expo , including building and maintaining native modules/bridges and managing JavaScript-to-native interoperability constraints (performance, threading, packaging/distribution).
• Expertise in Swift or Kotlin (expert in at least one) and the ability to contribute meaningfully across both iOS and Android codebases.
• Experience shipping production SDKs: API design, dependency management, packaging/distribution (e.g., SPM/CocoaPods, Gradle/Maven, npm), semantic versioning, and deprecation strategies.
• Proven ability to build reliable networked SDKs (REST/JSON, auth, retries, observability) with high-quality tests and automation.
• Practical security mindset and hands-on experience with secure storage / key management (Android Keystore, iOS Keychain / Secure Enclave).
• Excellent communication skills; able to collaborate with remote teams. English and Mandarin Chinese required.

Preferred Requirements:

• Experience contributing to a multi-language SDK ecosystem (e.g., Python ), including shared specs and a consistent developer experience across languages.
• Experience maintaining public-facing SDKs (including open-source or widely distributed libraries).
• Demonstrated ability to leverage AI-assisted development tools to accelerate delivery while maintaining quality, with clear evidence (e.g., faster PR iteration cycles, better test coverage, fewer regressions, stronger docs).

Circle is on a mission to create an inclusive financial future, with transparency at our core. We consider a wide variety of elements when crafting our compensation ranges and total compensation packages.
Starting pay is determined by various factors, including but not limited to: relevant experience, skill set, qualifications, and other business and organizational needs. Please note that compensation ranges may differ for candidates in other locations.
We are an equal opportunity employer. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status, veteran status, or disability status, or any other protected status required by the laws in the locations where we hire. Additionally, Circle participates in the E-Verify Program in certain locations, as required by law.
Should you require accommodations or assistance in our interview process because of a disability, please reach out to [email protected] for support. We respect your privacy and will connect with you separately from our interview process to accommodate your needs.
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