I apologize if this question is rather basic, but it is seems to be too broad to easily find a solution. I am running apache2 on Ubuntu on a VPS with 768MB of RAM. I am also running MySQL on the same machine. However, as my database grew in size, I ran into performance issues. I decided to try MongoDB. MongoDB is hosted on a separate server, so it should not affect anything on the web server. After I moved one of the tables to MongoDB, I did notice an improvement in performance. Last night, I converted more tables to MongoDB. Everything was working fine. However, this morning, the website was not reachable. Restarting apache solved the problem, but within 30 minutes I could not reach the site again.
I checked the apache error log and there was nothing suspicious there. What else should I look at?
Also, I don't even understand why this would be happening. Since I am moving some stuff off the server, there should be fewer issues, not more.