SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '4ea2cbcb720e0bf182987adf91afdb541960e8662cabd33eda8f0fe12cdfdf2d' 
  AND token = '6v8f7xRlGDBhtDVu7aGB1gdkuNRMlcuOXQ/zmtWDSgE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00009

JSON explain

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