SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6963c6352309111fe02c66df23c3498434cd2ab97ff02cec94f1790033cfbdca' 
  AND token = '6s9UuJ+yBfiUWJzYToBAsU6DsULZsDc9KJFmo9IWLrI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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