SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a20e81673b717c69d8fa585f04e03022aafef36945e1dd011d63271ce5c5fd75' 
  AND token = 'UE5PjdFGj2PMNV1cXQybPWz3/JlLqkSKvwRjR+LVCEs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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