SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '640a8010ff37ca9b51775a96fc3ea988b834fa44e2650e5498ed6b6c023d01d8' 
  AND token = 'MZxYo/QFx1v0cOwGYNb1mrCVeuZn6PQuxHZ+iRfgqFI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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