Dropbox does some rewriting

https://dropbox.tech/infrastructure/rewriting-the-heart-of-our-sync-engine

Rewrite dl.google.com in Go.

Google rewrote the service that serves chrome and other downloads in Go.

• Replace existing Cpp service with modern Go code.
• Rebuild the binary to meet existing unit tests
• Send traffic to both old and new services.
• Re-architect the system, collapse two different services into one.
• Advantages
  • cleaner maintainable code,
  • new service is faster as it can be concurrent and use more CPU cores.
  • It can use newer APIs of the dependent services -> e.g. file storage API

Lessons

• Don’t lock yourself to a line by line rewrite.
• Try to keep improving the architecture.

Slack Rebuilds the deskop client

Slack rebuilt their primary desktop app using React and a new multi team architecture.

Goals

Clients do not notice any different between clients. The interface is not defined in a spec, but still exists.

• Still, software codebases have life spans
• Rewrite to get away from legacy technologies - jQuery and dom manipulation.
• New technology pardigm (React) came along which was a step function improvement.
• Older app assumed a single app within a single process, that assumption was no longer true as lot of people are signed into multiple slack teams at any given point of time.
• Create a “modern” section of the codebase that would be future-proof.
• Rebuild the app piece by piece, have a way to use modern pieces in the existing app, so that you can get feedback on a smaller surface area.
• Conventional wisdom states that rewrites are best avoided, but sometimes the benefits are too great to ignore.
• Much easy to new use new technology like Service workers from the new codebase.