SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21cd635694a7aa3e4a2fd9db36d7b37f62e70204dfeb789f84bcd5a6a85a9fc1' 
  AND token = 'BfJrnIEDmmVdmJDOKC0rlM0h1WMKFBokYYCY/lNkRxs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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