Kodiak

Abstract

Turn's online advertising campaigns produce petabytes of data. This data is composed of trillions of events, e.g. impressions, clicks, etc., spanning multiple years. In addition to a timestamp, each event includes hundreds of fields describing the user's attributes, campaign's attributes, attributes of where the ad was served, etc. Advertisers need advanced analytics to monitor their running campaigns' performance, as well as to optimize future campaigns. This involves slicing and dicing the data over tens of dimensions over arbitrary time ranges. Many of these queries need to power the web portal to provide reports and dashboards. For an interactive response time, they have to have tens of milliseconds latency. At Turn's scale of operations, no existing system was able to deliver this performance in a cost effective manner. Kodiak, a distributed analytical data platform for web-scale high-dimensional data, was built to serve this need. It relies on pre-computations to materialize thousands of views to serve these advanced queries. These views are partitioned and replicated across Kodiak's storage nodes for scalability and reliability. They are system maintained as new events arrive. At query time, the system auto-selects the most suitable view to serve each query. Kodiak has been used in production for over a year. It hosts 2490 views for over three petabytes of raw data serving over 200K queries daily. It has median and 99% query latencies of 8 ms and 252 ms respectively. Our experiments show that its query latency is 3 orders of magnitude faster than leading big data platforms on head-to-head comparisons using Turn's query workload. Moreover, Kodiak uses 4 orders of magnitude less resources to run the same workload.