MySQL or JSON for data retrieval

Question

So, I have situation and I need second opinion. I have database and it' s working great with all foreign keys, indexes and stuff, but, when I reach certain amount of visitors, around 700-800 co-current visitors, my server hits bottle neck and displays "Service temporarily unavailable." So, I had and idea, what if I pull data from JSON instead of database. I mean, I would still update database, but on each update I would regenerate JSON file and pull data from it to show on my homepage. That way I would not press my CPU to hard and I would be able to make some kind of cache on user-end.

Answer 1

What you are describing is caching.

Yes, it's a common optimization to avoid over-burdening your database with query load.

The idea is you store a copy of data you had fetched from the database, and you hold it in some form that is quick to access on the application end. You could store it in RAM, or in a JSON file. Some people operate a Memcached or Redis in-memory database as a shared resource, so your app can run many processes or threads that access the same copy of data in RAM.

It's typical that your app reads some given data many times for every single time it updates the data. The greater this ratio of reads to writes, the better the savings in terms of lightening the load on your database.

It can be tricky, however, to keep the data in cache in sync with the most recent changes in the database. In other words, how do all the cache copies know when they should re-fetch the data from the database?

There's an old joke about this:

There are only two hard things in Computer Science: cache invalidation and naming things.

— Phil Karlton

Answer 2

So after another few days of exploring and trying to get the right answer this is what I have done. I decided to create another table, instead of JSON, and put all data, that was suposed to go in JSON file, in the table.

WHY?

Number one reason is MySQL has ability to lock tables while they're being updated, JSON has not.

Number two is that I will downgrade from few dozens of queries to just one, simplest, query: SELECT * FROM table.

Number three is that I have better control over content this way.

Number four, while I was searching for answer I found out that some people had issues with JSON availability if a lot of co-current connections were making request for same JSON, I would never have a problem with availability.