SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd21ae1495647afc52c968d167b5ba68f6b7c5ec0b77bad83453006aef3c07713' 
  AND token = '5itgvSu3cdrSdOtiR7NwfWFbY2n+3gqrPSAePQWERIE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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