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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b15bcff999f9771831fce24f9dd8b43813e4a6f4b592e4ab7e62671e0ceb60b5' 
  AND token = 'Xxtkhh2+ZSgy2p1zri0wfPvBdJ8QGtMEbrFSC6yw5Ak=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}