Google Student Blog: Intern Impact: Brotli compression for Play Store app downloads

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Intern Impact: Brotli compression for Play Store app downloads

February 6, 2017

This month, the Google Play team in our London office was hyped to welcome back Anamaria Cotîrlea, a former intern who is now a full-time software engineer. She joins us from Romania, where she studied in the Faculty of Mathematics and Informatics at Babeș-Bolyai University. As a software engineer at Google, Anamaria will be building upon the incredible impact she made as an intern on the Play team this past summer, when her work resulted in saving users an expected 1.5 petabytes (that's 1.5 million gigabytes) of data each day.

Back in 2015, Anamaria did her first internship with Google in Krakow, Poland. The technical skills she honed at that time set her up for her second Google internship this past summer with the Google Play team. During that internship, she integrated Brotli compression with the Google Play Store in order to streamline app installs and updates. This is hugely meaningful because Android users download tens of billions of apps and games on Google Play — totalling over 65 billion times (and growing), in fact!
It takes a lot of data to download new apps and updates to your existing apps, and we know users care about how much data their devices are using. Play is continually investing in making these installs and updates smaller, and in December 2016, we announced that we started using a new approach to delivering updates, known as File-by-File patching, which reduced the average update size to 65% smaller than the full app.
Anamaria’s project was to add support for Brotli for both new app installs and app updates. Brotli is a compression algorithm developed by Jyrki Alakuijala and Zoltán Szabadka of the Compression Team at Google Research Europe. Brotli was initially launched in 2015, offering enhancements in generic lossless data compression, especially when used for HTTP compression. Its compression rates, speed, and memory usage have been continuously improved, and it has proven to be a powerful tool for app compression, generally outperforming GZIP.
During her internship, Anamaria evaluated Brotli’s performance on our app library and made the changes necessary to our servers and the Play Store app to deploy Brotli for app delivery.
Here are a few examples of Brotli’s compression rate compared to GZIP’s:

Description	GZIP download size (MB)	Brotli download size (MB)	Percent Brotli saves over GZIP
Update Pinterest	4.64	3.70	20.27%
Update WhatsApp	5.75	4.73	17.63%
Install WhatsApp	13.95	13.04	6.52%
Install Pinterest	24.76	24.14	2.51%

Not only is this great news for our Android users, but it is also a terrific example of the real-life problems that Google interns are helping to solve, as well as the impact a Google intern can have in just a few short months. Brotli compression for app downloads is rolling out now, and users should start to enjoy the benefits over the coming weeks.

**A previous version of this blog didn't make it clear that Anamaria is now a full-time Googler. She is, and we've edited the blog to reflect that**