Exactly a year ago, Y Combinator graduate Realm launched a mobile database.
The developer world immediately devoured it, and hasn't stopped binging on it every since.
In March, when the company was just nine months old, Realm was already running on 100 million devices.
Today, the company says, it is powering 500 million.
That's because Realm has attracted the attention of some of the most popular mobile apps around including Pinterest, Groupon, and the BBC — "apps that millions and hundreds of millions of people use," Alexander Stigsen, co-founder and CEO, tells Business Insider.
"One out of every 10 apps being built today are being built on Realm and that’s increasing, very soon it will be closer to 2 in every 10," according to Stigsen's calculations.
Other companies using Realm include Buzzfeed, Intuit, Rite Aid, Zynga, Coinbase, Expensify, Wahoo Fitness, and Fortune 500 companies like banks and hospitals.
So what does Realm do, anyway?
The product is an "embedded" database that runs on your mobile device. These databases are hidden from users' view, but work closely with individual apps to let them store and read data created through the app.
Realm has zoomed to popularity as an alternative to a SQLite, another embedded mobile database, which also runs in every phone and web browser, and is a popular choice for iPhone and Android apps.
SQLite is popular in part because its a rare form of software that's even more "free" than free and open source software. It's code was completely donated to the public domain. No one needs a license of any kind to use it. It's maintained by volunteers at the SQLite Consortium.
But some developers say that Realm is easier to learn and runs much faster.
Its popularity has skyrocketed in the past few months in particular because companies are "moving to mobile very fast," Stigsen says.
Every company these days is creating mobile apps and bigger companies are building up to 30 apps apiece to be used by customers, employees, and business partners.
This is great news for companies that cater to mobile app developers, from Realm to Xamarin (which provides easy tools for traditional developers to write to mobile platforms).
Stigsen created Realm with his childhood friend Bjarne Christiansen when they both worked as engineers at Nokia. At that time, they discovered a way to make data use less memory on a phone, so apps would work faster, which eventually led them to build a new database.
Realm last spring raised $20 million led by Khosla Ventures and Scale Venture Partners. It's raised $29 million to date, and other backers include Andreessen Horowitz, Greylock, Redpoint, Ignition, SVAngel, Data Collective and more.
