Most of Slack runs on a monolithic service called "The Webapp" with hundreds of developers making hundreds of changes weekly. Deploying at this scale poses a unique challenge, especially in implementing continuous deployment. Slack deploys from its Webapp repository 30-40 times a day to its production fleet, with a median deploy size of 3 PRs, managed by ReleaseBot for automation. Monitoring deployments for anomalies is crucial, with z scores and dynamic thresholds used by Slack to detect anomalous behavior during deployments.
