I met the same problem when I tried to run a wordpress on my micro instance without RDS.
Adding a Swap page solved the problem for me.
You can follow this to setup the swap page:
If it still doesn't work for you, consider using the RDS service.
The link to the blog sometimes fails. I copied the content below for the record. Credit goes to the blog author Pedram Moubed:
Amazon EC2 Micro Instance Swap Space - Linux
I have a Amazon EC2 Linux Micro instance. Since Micro instances have only 613MB of memory, MySQL crashed every now and then. After a long search about MySQL, Micro Instance and Memory Managment I found out there is no default SWAP space for Micro instance. So if you want to avoid the crash you may need to setup a swap space for your micro instance. Actually performance wise is better to enable swap.
Steps below show how to make a swap space for your Micro instance. I assume you have AWS Account with a Micro instance running.
dd if=/dev/zero of=/swapfile bs=1M count=1024
- Add this line
/swapfile swap swap defaults 0 0to
Step 4 is needed if you would like to automatically enable swap file after each reboot.
Some useful command related to SWAP space:
$ swapon -s $ free -k $ swapoff -a $ swapon -a