A startup launched 9 months ago by these former Nokia engineers is going absolutely bonkers

Nine months ago, Y Combinator graduate Realm launched a mobile database and the world went instantly nuts for it.

Today the company says its database is already running on 100 million devices.

That makes it the second-most deployed database in the world, by the calculations of Alexander Stigsen, co-founder and CEO.

That's because this is an "embedded" database that runs on your mobile device. The databases built by companies like Oracle, Microsoft or MongoDB, are far bigger and more powerful and service millions of applications and billions of people, but they run on fewer devices. They run on computer servers.

Such traditional databases "run on at most a few dozen million servers," Stigsen tells us. So that makes Realm No. 2 to SQLite, another embedded mobile database, which "runs in every phone and web browser."

Realm wants to take down SQLite, which is the mobile database recommended by Apple for iOS and Google for Android. SQLite is a rare form of software. It is even more "free" than free and open source software because its code was donated to the public domain. No one needs a license of any kind to use it. It is maintained by volunteers at the SQLite Consortium.

But SQLite is clunky to use. "SQLite was designed over 15 years ago for use on board the US Navy's guided missile destroyers," Realm investor and new board member Andy Vitus wrote in a blog post. (Vitus is a partner with Scale Venture Partners.)

Realm is not only easier to learn but also up to 100-times faster, Vitus says.

It was the brainchild of Stigsen and his childhood friend Bjarne Christiansen from Denmark from their days when they were engineers at Nokia. While at Nokia, they discovered a way to make data use less memory on a phone, so apps would work faster. That discovery led them to take on SQLite and invent a new mobile database.

And some of the biggest names in the Valley noticed. On Tuesday Realm announced that it raised $20 million led by Khosla Ventures and Scale Venture Partners ($29 raised to date).

Realm's customers include Groupon, Buzzfeed, Intuit, Rite Aid, Zynga, Coinbase, Expensify, Wahoo Fitness, and Fortune 500 companies like banks and hospitals.

Other investors include Andreessen Horowitz, Greylock, Redpoint, Ignition, SVAngel, Data Collective and more.