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June 14, 2016
by Will Maier

Building Confidence

For more than a year, we’ve been building and testing a replacement for the most complex and important part of Simple—our banking platform.
Group Work 1

Today, we’re ready to welcome all new customers onto Simple accounts backed by BBVA Compass. This is our biggest project yet and it took hundreds of people countless hours to make sure that the new platform was working safely and reliably.

To build and test something this big with confidence, we used familiar techniques and developed a few new ones.

Whatever the project, when you start something massive, the end goal can seem impossibly distant and unreachable. Engineers are people, too, and we do our best work when we can see the positive impact we’re having on our customers. Since this project would require months of work before we could even begin testing, we designed a sequence of milestones to help track our progress. The completion of each milestone gave us a chance to celebrate being one step closer to sharing our work with you.

TC – Project Days

We celebrated our first big company milestone back in 2012, when we launched Simple to customers. In a time when most banking platforms still ran ancient code on very large, very expensive mainframe systems, we knew that ours needed to be different. So we built an independent service to handle each of the core functions that make Simple work. This architecture made it possible to quickly build and deploy new features like Goals and Photo Check Deposits.

TC – death star

We began our work on the new platform by designing services to match the existing features. Imagine an artist using a real-life landscape as the basis for a painting, comparing what they’ve created with the real thing as they work. For each change we made, we could compare the old with the new and verify that things matched. We designed each change to be as small as possible and made sure to land the changes in production quickly. Deploying small changes to production frequently reduces the risk and complexity of each change and allows us to move more quickly and safely. In fact, we deployed the first pieces of the new platform to production back in 2015 and have been iterating ever since.

This incremental approach also made it possible for employees to use the new platform—“dogfood,” wherein we use our own product to quality test —after a few months of development rather than waiting until the build was complete. We aren’t just Simple employees, we’re Simple power users, so we can leverage our experience to test. In fact, by the time we started opening customer accounts on Compass nearly 75% of our employees were on the platform. We encouraged all those folks to test by setting up an internal bug bounty program and awarding the most active testers with swanky pins and shirts. Not long after that we were ready to invite our friends and family to join us on the new platform. Soon, hundreds of people relied on their Simple account backed by BBVA Compass for their day-to-day banking.

TC – bug squasher

We usually ship incremental changes to production and dogfood new features at Simple, though applying them to this project required a few tweaks. Because of the size and complexity of the project, we wanted to do even more to make sure everything was working the way it should. Just like we were able to test and validate features side-by-side on the two platforms, our data team developed a new set of tools to compare the behavior of groups of customers simultaneously across both platforms.

First, they identified metrics that captured the overall experience of using Simple: how long it took to sign up; how often customers needed help from our CR team; how often they created Goals. For each of these measures, the data team defined a hypothesis about how the measure should behave as real customers started using the new Simple. And because we were running the two platforms side-by-side, we could split new customers as they joined Simple and make a direct comparison of their behavior across the two platforms. The data team held on giving the green light until they had enough data to confirm a result. Today, all of those measures show that the new platform works as well as — or better than — the old one.

TC – chart

We used all of these tools, familiar and new, to make a big and complex project seem achievable. Our first platform supported the hundreds of thousands of customers that have joined us in the last four years. We’re excited to welcome many more customers onto our new platform and to use it as the foundation to continue to make Simple even better.

Disclaimer: Hey! Welcome to our disclaimer. Here’s what you need to know to safely consume this blog post: Any outbound links in this post will take you away from Simple.com, to external sites in the wilds of the internet; neither Simple nor our partner banks, The Bancorp Bank and BBVA Compass, endorse any linked-to websites; and we didn’t pay/barter with/bribe anyone to appear in this post. And as much as we wish we could control the cost of things, any prices in this article are just estimates. Actual prices are up to retailers, manufacturers, and other people who’ve been granted magical powers over digits and dollar signs.