SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '340390e02c5b38136233deff2fe12b1efbec7945bcc058999c765c34fe217fca' 
  AND token = 'QoYYjpHT4JEyc8Oi7jF2yq6qx2cx1XZ5AgMhQtL0+gA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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