Twitter’s annual project summary, the data is touching, what code can reduce 600,000 lines and save 100 million US dollars?

The official Twitter account released a year's project summary . Highlights include:

Completely restructured the For you service and ranking system, reducing the number of lines of code from 700K to 70K, a 90% reduction, reducing computing usage by 50%, and increasing post throughput by 80%.
The API middleware layer of the technology stack was restructured and the architecture was simplified , removing more than 100,000 lines of code and thousands of unused internal ends, and eliminating unused client services.
Closed the Sacramento data center and reconfigured 5,200 racks and 148,000 servers, saving more than $100 million annually.
Post-metadata retrieval delays were reduced by 50%, and global API timeout errors were reduced by 90%.
Optimized use of cloud service providers to do more work locally, reducing monthly cloud costs by 60%. Specifically, all media/blob artifacts are moved out of the cloud, reducing the overall cloud data storage size by 60%. At the same time, cloud data processing costs have been reduced by 75%.
Build a local GPU supercomputing cluster and design, develop and deliver a 43.2Tbps new network fabric architecture to support the cluster.
Expand network backbone capacity and redundancy, saving $13.9 million annually.

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