Stash

Company Background

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Stash is a personal finance and investing app designed to make wealth-building more accessible for millions of Americans. As a fast-scaling fintech company, Stash helps users save, invest, and automate financial habits through an easy-to-use digital platform. With a growing customer base and product roadmap, the engineering team has continuously evolved its infrastructure to meet increasing demands on performance, scale, and flexibility.

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The Challenge

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As Stash’s engineering organization scaled rapidly, their monolithic Rails application began to slow down development velocity—especially when coordinating cross-team deployments. To address this, the team began decomposing the monolith into microservices built in Scala.

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One of the first critical initiatives supported by this new architecture was Auto-Stash, a feature that enables users to set up recurring deposits into their investment accounts. At the heart of this feature was a new transfer scheduling service—a component that needed to account for numerous edge cases and function seamlessly from day one. A failed launch would not only impact product performance but could erode user trust in an investment experience designed to be simple and automated.

The Solution

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Stride embedded senior engineers within Stash’s team to help deliver the recurring transfers service—a key backend component of Auto-Stash.

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Independently Deployable Service

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Stride collaborated on the design and delivery of a Scala-based microservice tailored for Stash’s distributed systems architecture. The service was built to be independently deployable, ensuring it could scale with the business and integrate cleanly into the growing microservices ecosystem. Extensive unit testing was implemented to cover edge cases and safeguard reliability.

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Decoupled Microservice Communication

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The service was designed to store and manage user-defined scheduling preferences. At regular intervals, it queried its datastore for scheduled transfers and made that data available to another service responsible for evaluating and publishing eligible events to an SQS queue. This modular, decoupled architecture supported long-term scalability while reducing the risk of system-wide dependencies.

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The Business Outcomes

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In just three months, Stride and Stash successfully delivered a robust, scalable scheduling service that powered the launch of Auto-Stash.

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Upon release, Auto-Stash allowed millions of Stash users to automate their recurring investments—removing friction from the investing process and helping more Americans build consistent financial habits. By enabling seamless, scheduled money movement, the new service became a foundational element in Stash’s mission to support long-term wealth-building for everyday investors.

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This content is for informational purposes only. Investment advisory services offered by Stash Investments LLC, an SEC registered investment adviser.

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