SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '638648208ca3f2cbf0de1c8f148ef1eba1d2539ad0d903414f64acf4a5a9682f' 
  AND token = 'NsGSgnUmjAkiP/Jsonc9GwFZAY4gVXNzZhRBQiQRHsY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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