Behind the scenes of a real-time ad auction on the web.
A small technological marvel occurs on almost every visit to a web page. In the seconds that elapse between the user’s click and the display of the page, an ad auction takes place in which hundreds of bidders gather whatever information they can get on the user, determine which ads are likely to be of interest, place bids, and transmit the winning ad to be placed in the page.
How can all that happen in approximately 100 milliseconds? Let’s explore the timeline and find out what goes on behind the scenes in a modern ad auction. Most of the information I have comes from two companies that handle different stages of the auction: the ad exchange AppNexus and the demand side platform Yashi. Both store critical data in an Aerospike database running on flash to achieve sub-second speeds.