MySQL on DigitalOcean Servers Crashing

The smalles instance of a DigitalOcean droplet only provides 512GB of RAM. Do not forget that this rather low in comparison with other Web servers. If you do not check your configuration files for Apache and MySQL and leave them at defaults, you can easily run out of memory, because DO droplets come without swap by default. In the case of MySQL, your will be confronted with this error message:
InnoDB: Fatal error: cannot allocate memory for the buffer pool
The solution is rather simple, as provided by a comment in the support forum. Just follow this guide in order to enable some swap space. As the system is completely on a SSD, you should not have a huge performance impact.