+=item publicinbox.indexSequentialShard
+
+For L<public-inbox-v2-format(5)> inboxes, setting this to C<true>
+allows indexing Xapian shards in multiple passes. This speeds up
+indexing on rotational storage with high seek latency by allowing
+individual shards to fit into the kernel page cache.
+
+Using a higher-than-normal number of C<--jobs> with
+L<public-inbox-init(1)> may be required to ensure individual
+shards are small enough to fit into cache.
+
+Warning: interrupting C<public-inbox-index(1)> while this option
+is in use may leave the search indices out-of-date with respect
+to SQLite databases. WWW and IMAP users may notice incomplete
+search results, but it is otherwise non-fatal. Using C<--reindex>
+will bring everything back up-to-date.
+
+Available in public-inbox 1.6.0 (PENDING).
+
+This is ignored on L<public-inbox-v1-format(5)> inboxes.
+
+Default: false, shards are indexed in parallel
+
+=item publicinbox.<name>.indexSequentialShard
+
+Identical to L</publicinbox.indexSequentialShard>,
+but only affect the inbox matching E<lt>nameE<gt>.
+