Thanks for mentioning! One of the most fun parts of this series I think is handling indexes on INSERT and actually making use of them based on (effectively) pattern matching on WHERE clauses.
> (Use the tag "sql" to find the later parts. Sadly not linked directly from that first one.)
There's a "Note" section right below that title that links to the other posts. :) I guess it is UX feedback that this was not obvious to spot.