Realm

Overview

Realm rebuilt mobile persistence around application objects and offline operation. Founded in 2011 by former Nokia engineers Alexander Stigsen and Bjarne Christiansen, the Summer 2011 YC company spent years building a mobile-native database core before launching publicly in 2014.^[1]

MongoDB agreed to acquire Realm for $39 million in cash in April 2019 and closed in May.^[2][3] The product had two afterlives. Realm's local database remained open source, while MongoDB retired Atlas Device Sync and related App Services on September 30, 2025.^[4] The acquisition was strategically coherent; the hosted service's later retirement does not mean all Realm technology failed.

Founding Story

Stigsen and Christiansen founded the company under the tight.db identity after working at Nokia.^[1] They joined YC in 2011, then stayed in stealth for several years to build a new database engine for mobile devices.

“Building a database takes a long while,” Stigsen said in 2015.^[5] The delay reflected the scope of the bet. Realm was not a wrapper around an existing service. It was an embedded database designed to fit inside applications, remain available offline, and expose application objects without the mapping and persistence boilerplate associated with SQLite or Core Data.

The public product launched in 2014. Its small footprint, local speed, and developer ergonomics helped it spread through mobile projects before the company added cloud synchronization.

The founding sequence matters. Realm first earned adoption as a local component that developers could use without a hosted dependency. The later Object Server and Synchronization Platform added a commercial cloud layer, but the local database retained an independent technical identity.

Timeline

• 2011: Stigsen and Christiansen founded tight.db and joined YC's Summer batch.^[1]
• 2014: After years in stealth, the company publicly launched Realm.^[5]
• March 2015: Realm raised $20 million, bringing reported total funding to $29 million. It said the database ran on 100 million devices.^[5]
• Later: Realm added Object Server and a Synchronization Platform for two-way device-to-cloud sync.^[6]
• April 24, 2019: MongoDB announced a definitive agreement to acquire Realm for $39 million cash, subject to adjustments.^[2]
• May 7, 2019: MongoDB completed the acquisition of Tightdb, Inc.^[3]
• September 2023: MongoDB renamed Realm SDKs as Atlas Device SDKs and said the local SDKs would remain Apache 2.0 and usable without Atlas.^[7]
• September 30, 2025: Atlas Device Sync and related App Services reached end of life.^[4]

What They Built

Realm embedded a sub-one-megabyte object database inside mobile applications. Data remained available locally and offline without calls to an external service.^[5] Developers worked with application objects directly instead of translating between object models and relational tables.

This put Realm against SQLite and Apple's Core Data at the persistence layer. It competed on developer experience, performance, and offline behavior rather than a cloud API alone.^[1]

Realm later added Object Server and a Synchronization Platform. The hosted layer moved changes between devices and cloud, supporting an offline-first application that could reconnect and converge.^[6] That broadened the business from an embedded component into a cloud-to-device stack.

MongoDB integrated Realm with Atlas and Stitch, then renamed the SDKs as Atlas Device SDKs.^[7] When hosted sync retired, local database code continued through open-source and community branches. Atlas-specific sync code required removal or migration. The distinction is essential: embedded storage continued; the managed synchronization control plane did not.

Market Position

Target Customers

Realm targeted mobile developers who needed fast local persistence, offline operation, and less boilerplate. The sync platform later targeted teams building applications that needed cloud-to-device convergence.

Market Size

No audited revenue, margin, retention, or customer-concentration figures were found. In March 2015, Realm said it ran on 100 million devices and named Groupon, BuzzFeed, Intuit, Zynga, Coinbase, and Expensify.^[5] At acquisition, MongoDB reported more than 100,000 active developers and more than two billion downloads.^[2] These are company-reported figures.