借助MySQL和Apache，从服务器获得更快的响应

I just want to know which process is fast and how (in core) flow works.

About system: I have a user information add and edit system inside back end of application admin.I just want to show (Read-only) information on Android application using APIs.

Flow:

  1. At admin side user information will add and edited.

  2. After add process mysql return primary Key of user inserted data (LIKE 123) and using that primary key I make a json file (LIKE 123.json) at a particular location on same server.

  3. In edit process I overwrite that file using same primary key.

Here is my question: (2 cases)

Case 1: When API hit server with user primary key (LIKE 123).
(1).PHP initialized.
(2).MYsql connection create, Query fire to mysql, get data and make a json of that same data and return to API, close Mysql connection.

Case 2: When API hit server it just call same file which I was created at time of add or Edit with a absolute URL
LIKE: www.DOMAIN.COM/json-file-path/123.json and return back to Android. (I amused that in this case PHP and MYSQL is not even initialized only Apache initialized )

Now in both of cases

1) Which case is fast and best ?
2) How internally this (mysql, PHP, Apache) will work ?
3) In both of case and which one Should I use?