SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50ad6334f71afcfa0b4c77ab1f96a06b6727a6663a9d710b104c424e97be6398' 
  AND token = 'v4lTyjGKozehLF6+YINV5BwLk9nr7dwXnKhUAFBtpC4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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