Berkeley DB with a header date of 1994 :) In base, and of course it still works.
Sqlite was removed from base, again, in 6.1 (2019) --https://www.openbsd.org/faq/upgrade61.html
with this BSDCAN '18 pdf briefly explaining the issues (unmaintainable) -- https://www.openbsd.org/papers/bsdcan18-mandoc.pdf