ssb: That's just a weird formulation of this query. I saw it in a profile.

metadata/en-US/changelogs/34.txt

@@ -0,0 +1,10 @@
+* The connections tab now shows replication progress.
+* Replication performance and thoroughness improvements.
+* Bind only to localhost on mobile, configurable.
+* Request blobs referenced by referenced blobs, and improve performance of that
+  query.
+* Fix file upload on iOS.
+* Add rough back/forward/refresh buttons on iOS.
+* Other crash fixes and performance improvements.
+* Updates:
+  * CodeMirror

src/ssb.db.c

@@ -981,7 +981,7 @@ bool tf_ssb_db_get_latest_message_by_author(tf_ssb_t* ssb, const char* author, i
 	bool found = false;
 	sqlite3_stmt* statement;
 	sqlite3* db = tf_ssb_acquire_db_reader(ssb);
-	const char* query = "SELECT id, sequence FROM messages WHERE author = ?1 AND sequence = (SELECT MAX(sequence) FROM messages WHERE author = ?1)";
+	const char* query = "SELECT id, sequence FROM messages WHERE author = ?1 ORDER BY sequence DESC LIMIT 1";
 	if (sqlite3_prepare(db, query, -1, &statement, NULL) == SQLITE_OK)
 	{
 		if (sqlite3_bind_text(statement, 1, author, -1, NULL) == SQLITE_OK && sqlite3_step(statement) == SQLITE_ROW)