Cash Engineering Principles

Nif Ward

In 2022, we set out to capture our current Engineering Principles: how high-performing engineering teams do their best work at Cash. We’re proud of the work we did to record...

Molecule: Build a StateFlow stream using Jetpack Compose

Benoît Quenaudon

Molecule allows you to write imperative reactive code! This is a game changer!

Synchronize Dependencies with BOM

Benoît Quenaudon

Keeping multiple dependencies of the same group in sync can be tricky. BOM makes it safe.

Rx to Coroutines Concepts, Part 5: Shared Flows

Bill Phillips

Sometimes, you need to share a Flow with multiple consumers. Read all about how this works in this post.

Rx to Coroutines Concepts, Part 4: Cold Flows

Bill Phillips

In this post, everything you could ever need to know and more about how cold Flows work.

The state of managing state (with Compose)

Jake Wharton

Five years ago the Cash App Android client started splitting our UI rendering and UI presenter responsibilities into distinct types. We had leaned into RxJava heavily in the years prior,...

Rx to Coroutines Concepts, Part 3: Deferred & Channels

Bill Phillips

In this post, we'll cover the foundations of coroutines communications with Deferred and Channel.

Rx to Coroutines Concepts, Part 2.1: Exceptions

Bill Phillips

Okay, so there's a bit more to know about structured concurrency. This short-ish addenda covers how exceptions propogate within structured concurrent code.

Rx to Coroutines Concepts, Part 2: Structured Concurrency

Bill Phillips

Everything you could possibly want to know about structured concurrency is in this post.

Obsolete code is slowing you down

Michael Druker

As engineering teams, an important measure of our effectiveness is how quickly we are able to build. If we can realize an idea more quickly, we can do more. While...

Sharp Edges in Kotlin Coroutines Testing Tools

Kevin Cianfarini

At Cash App, we’re starting to integrate Kotlin coroutines into our app architecture. My coworker Bill, who has taken interest and ownership in this migration, came to me the other...

Gradle dependency license validation

Jake Wharton

Six years ago we added a screen to the Android Cash App to display the open source libraries we use and their licenses. This screen had to be updated manually,...

Migrating from Burst to TestParameterInjector

Jake Wharton

Square’s Burst library burst onto the scene in 2014 stemming from general dissatisfaction with JUnit 4’s built-in parameterized runner. It enabled the use of enums to vary input to your...

Rx to Coroutines Concepts, Part 1

Bill Phillips

The reactive paradigm is powerful, but can also be obscure. Coroutines provide an alternative paradigm that is better in every way.

Great teams merge fast

Saket Narayan

One of the many things I was constantly amazed about during my first few weeks at Square/Cash App was seeing how fast this team shipped code. All members of the...

AssistedInject is dead, long live AssistedInject!

Jake Wharton

After ~5 years of existing and ~4 years as an open source project, our AssistedInject library has been deleted. Mourn not, however, for the same functionality is now available directly...

protoc-gen-grpc-gateway-ts - Clean, Idiomatic TypeScript for grpc-gateway

Yun Lai

protoc-gen-grpc-gateway-ts is a TypeScript client generator for the grpc-gateway project. It generates idiomatic TypeScript clients that connect the web frontend and golang gRPC backend fronted by grpc-gateway.

Rolling Out Org-Wide Changes

Saman Alvi

Cash App has grown into a complex engineering organization. Our team of hundreds of engineers deploys dozens of services to AWS multiple times a day. Our teams span several time...

Investigating Crashes with Aardvark

Nick Entin

Crashes can be one of the most straightforward types of issues to debug. There are many different categories of crashes that can happen on iOS - everything from bad memory...

Debugging UI Issues with AardvarkReveal

Nick Entin

Reports of UI issues can be difficult to debug when the issue is not easily reproducible. Bug reports created through Aardvark include a screenshot of the app at the time...