SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '923bb441435d10e10eedad19c78de92ad05365c472f08758db55320e21149ef3' 
  AND token = 'PWLZWP1eDY7jPD9URPUZ2UYvXLTj8DRmrklvw+XPvGw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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