SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '88064fe47164c2d462cd9ef8483859014309292a97ecea4c261f5c548c14fd51' 
  AND token = '/myHjp8cHHWJUqQ3901Ed+wZEpHtZnQMhjaMONLsY58=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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