Evernote Architecture - 9 Million Users and 150 Million Requests a Day
Monday, May 23, 2011 at 8:33AM
Todd Hoff in Example

The folks at Evernote were kind enough to write up an overview of their architecture in a post titled Architectural Digest. Dave Engberg describes their approach to networking, sharding, user storage, search, and some other custom services.

Evernote is a cool application, partially realizing Vannevar Bush's amazing vision of a memex. Wikipedia describes Evernote's features succinctly: 

Evernote is a suite of software and services designed for notetaking and archiving. A "note" can be a piece of formattable text, a full webpage or webpage excerpt, a photograph, a voice memo, or a handwritten "ink" note. Notes can also have file attachments. Notes can then be sorted into folders, tagged, annotated, edited, given comments, and searched. Evernote supports a number of operating system platforms (including Android, Mac OS X, iOS, Microsoft Windows and WebOS), and also offers online synchronization and backup services.

Key here is that Evernote stores a lot of data, that must be searched, and synced through their cloud to any device you use. 

Another key is the effect of Evernote's business model and cost structure. Evernote is notable for their pioneering of the freemium model, based on the idea from their CEO: The easiest way to get 1 million people paying is to get 1 billion people using. Evernote is designed to become profitable at a 1% conversion rate. The free online service limits users to a hefty 60 MB/month while premium users pay $45 per year for 1,000 MB/month. To be profitable they most store a lot of data without spending a lot of money. There's not a lot of room for extras, which accounts for the simple practicality of their architecture. 

The article is short and succinct, so definitely read it for details. Some takeaways:  

There's a promise of future articles focusing more on individual subsystems. I look forward to these as you have to appreciate the elegance of the system they've created for their business model. A good example to learn from.  

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