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by cantlin 3833 days ago
The strategy of proxying real usage to a second code path is incredibly effective. For months before the relaunch of theguardian.com, we ran traffic to the old site against the new stack to understand how it could be expected to perform in the real world. Later of course we moved real users, as incrementally as we possibly could.

The hardest risk to mitigate is that users just won't like your new thing. But taking bugs and performance bottlenecks out of the picture ahead of time certainly ups your chances.
2 comments
bertr4nd 3832 days ago
Out of curiosity - when you've done this type of proxy test, what do you do about write operations? Do you proxy to a test DB, or do you have your code neatly factored to avoid writing on the test path (I guess most code I've worked on that needed a rewrite also wasn't neatly factored :) ).
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geoka9 3832 days ago
> The hardest risk to mitigate is that users just won't like your new thing.

Do they ever? Why change the part users are used to?

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