SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8b5d99d9c45420cc6755d0608fe05e18ace7d202236a2af572330da874cf520' 
  AND token = 'NKVBSe4ipwR57x2UUDm2r3vHUCJJSDje2dRIuy4DLFw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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