Looks great!

Reviewed 4 of 4 files at r1, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @RaduBerinde)

checkpoint.go line 50 at r1 (raw file):

// that don't overlap with any of these spans are excluded from the checkpoint.
// Note that the checkpoint can still contain keys outside of these spans (from
// the WAL and from SSTs that partially overlap with these spans).

nit: maybe add a word of warning that any keys outside the specified spans that do make it into the checkpoint may be inconsistent: iterating over the checkpoint outside the checkpoint spans may surface keys that were deleted or overwritten, etc.

checkpoint.go line 76 at r1 (raw file):

		case cmp(f.Smallest.UserKey, s.End) >= 0:
			// File range starts after range of interest
		case cmp(f.Largest.UserKey, s.Start) < 0:

a file's largest bound can be exclusive if the file contains range tombstones or range keys that have an exclusive end at f.Largest.UserKey. If f.Largest.IsExclusiveSentinel() and cmp(f.Largest.UserKey, s.Start) == 0, the file f does not contain any keys containing s.Start.

TFTR!

Reviewable status: 1 of 5 files reviewed, 2 unresolved discussions (waiting on @jbowens)

checkpoint.go line 50 at r1 (raw file):

Good point, done.

checkpoint.go line 76 at r1 (raw file):

Done, extracted this logic out from some existing code.

Reviewed 1 of 1 files at r3, all commit messages.
Reviewable status: 2 of 5 files reviewed, all discussions resolved (waiting on @RaduBerinde)

checkpoint.go line 76 at r1 (raw file):

Nice