Not much. Use an LTS version of a distribution which you understand well. You're more likely to have appsec problems caused by yourself rather than being compromised by problems in the OS.
Make sure you're able to do firedrills like e.g. upgrading the version of Nginx or OpenSSL which you use in response to a vulnerability in them getting discovered. We've been doing a lot of that these last two years, and it probably won't get any less common.
Make sure you're able to do firedrills like e.g. upgrading the version of Nginx or OpenSSL which you use in response to a vulnerability in them getting discovered. We've been doing a lot of that these last two years, and it probably won't get any less common.