Software Rewrites

Dropbox does some rewriting

Rewrite 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


  • 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.


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.