Sudden load, planned or otherwise.
BEFORE A PLANNED SPIKE
Confirm caching is working, and that cacheable pages are actually being served from cache Consider temporarily increasing resources Put a CDN in front Test under load if the event matters
DURING AN UNEXPECTED SPIKE
Determine whether the traffic is legitimate. Check the access log for patterns: one address making thousands of requests is an attack, not success.
If illegitimate, block the source or enable a challenge through a CDN.
If legitimate, ensure caching is serving as much as possible and consider scaling.
EMERGENCY MEASURES
Enable aggressive caching temporarily
Disable expensive features: search, live chat, real-time widgets
Serve a static holding page for the heaviest sections Rate-limit at the web server
WHAT NOT TO DO
Restart services repeatedly, which drops connections and makes things worse.
AFTERWARDS
Review what limited you. Usually memory or an uncached expensive page. Fix that before the next event.
PLANNING AHEAD
A CDN in front of the site absorbs most of this and is worth having permanently.
