In version 0.2.18, We resolved a severe performance regression that has existed since 0.2.15. The issue was related to code generation for constant strings and literals, and could cause slowdowns of 1-3 orders of magnitude. Nearly every large pipeline used these features in some way, but some pipelines would have been affected much more than others.
This issue has exists in versions 0.2.15, 0.2.16, and 0.2.17, and any users on those versions should update as soon as possible.
As always, see the change log for full patch notes.