Hello, I am looking for advice concering inconsistent query results. Problem: We are observing queries that return inconsistent query results. The query in question selects records within a period of time (e.g., month) based on a datetime column. The result set is missing random records within the queried time period. It appears that the inconsistent result is produced when the query uses an index containing the datetime column. When the index is not used, the result seems to contain all records. Dropping and recreating the index caused the result to be complete again. However, this has NOT solved the problem permanently as the wrong behaviour has reappeared afterwards. On second appearance, we have used OPTIMIZE table on the table in question which has again resolved the problem, we will have to wait to see whether the problem occurs again. CHECK TABLE returned no erros for the affected table. The problem does not seem to be limited to one installation, we are seing it on different MariaDB installations. Questions: - Has anybody seen such behaviour in the past? - How can we diagnose the problem? Environment: - MariaDB Version: MariaDB 10.5.13 - MariaDB Storage engine: InnoDB - MariaDB Collation: utf8mb4_unicode_ci - OS: Windows Server Kind regards, Jef