php web application architecture

I am building an internal invoicing platform (PHP and SQL)which would mostly interact to the database to read/write data. So the idea is to get some data from the databse and assign it to a particular tab. I have ~ 10 tabs and x amount of data to be read, which is growing on a constant pace. To limit the calls to database and improve the speed I am thinking of: 1. Have one call to the database 2. Create the buckets and save them in session 3. When some cells are updated by the user on the webpage I would update that row in the db and would not make a call to create new session, but instead update the current session variables and reasign the buckets. 4. Only one person will be working on this platform.

Is this a reasonable approach in terms of design and performance? Also, if there would be more people working on this platform in the future it would "break down", so I am also open to multi-person design suggestions.