iOS first, Android optional

How you will make an impact

ThredUp is changing the way people shop and think about used fashion. Our iOS app is the primary way millions of customers discover and purchase used clothing, making it one of the most important drivers of our business. As a Senior iOS Engineer, you will play a pivotal role in enhancing and evolving this application — stabilizing the platforms, modernizing the architecture, and shaping new features that provide seamless and enjoyable experiences for our users.

Reporting to the Core Ecomm Engineering Director, you will join a small team that works cross-functionally and owns the end-to-end shopping journey – from first checkout to checkout and post-purchase. Your business will directly impact growth and retention, improving reliability while building the foundation for new product innovations.

We are looking for a collaborative, impact-driven engineer who is passionate about delivering stable, efficient, customer-focused applications. This candidate must have the technical excellence and pragmatism to tackle challenging problems, balancing strategic architectural investment with the need to ship quickly.

In this role you will get

• Own and optimize the core areas of ThredUp for iOS, ensuring performance, stability, and scalability across critical user flows (onboarding, browsing, checkout, promotions, and subsequent ordering).
• Leverage crash reporting and performance monitoring tools (e.g., Instruments, Crashlytics, Sentry) to proactively identify and resolve issues.
• Collaborate closely with product managers, designers, and engineers across disciplines to deliver impactful features that improve customer trust, conversion, and retention.
• Contribute to the architectural modernization of the application, providing patterns and best practices that accelerate development speed.
• Discover strategies to reduce redundant development and improve speed across mobile platforms (e.g., Kotlin Multiplatform), while maintaining a high-quality native iOS experience.

What we are looking for

• 8+ years of professional experience in developing large-scale native iOS applications.
• Deep experience with Swift and Objective-C, with strong knowledge of UIKit and working knowledge of SwiftUI, with experience in modern iOS architectural patterns.
• Strong experience in concurrency, memory management, performance tuning, monitoring, and observability.
• Proficiency in working with REST APIs, GraphQL, networking, and data integration.
• Experience working with continuous integration and release pipelines for iOS applications.
• Product Mindset: The ability to link technical decisions to user experience and business outcomes.
• Curiosity and excitement about leveraging AI to accelerate mobile development (e.g., code generation, testing, performance optimization).
• Familiarity with Android (Kotlin/Java) and interest in collaborating with Android engineers to ensure platform parity is a plus.
• Exposure to Kotlin Multiplatform or other shared code strategies, along with experience in consumer-facing e-commerce, search, or other large-scale user engagement applications is a plus.
• Experience mentoring peers or leading feature-level initiatives is a plus.