It takes about 20 minutes to pull the docker image and 10 minutes to perform the build + tests:
https://dev.azure.com/cncf/4684fb3d-0389-4e0b-8251-221942316e06/_apis/build/builds/46369/logs/103

From:
https://dev.azure.com/cncf/envoy/_build/results?buildId=46369&view=logs&j=2d2b3007-3c5c-5840-9bb0-2b1ea49925f3&t=168f295b-0553-5364-35f7-923225ecd8b3

Because we run everything in RBE, it is possible to run a smaller image in AZP (only bazel + a few deps for extracting dependencies).

Not a high priority but just for tracking.

cc @wrowe @sunjayBhatia