I have campaigns I've been running CPC for a while with a fixed daily budget that I have had 0 problems with. Never went over, never had huge spikes and never crashed my web server.
Last week I log in to AdWords and I have recommendations to switch to CPA on a specific campaign. I switch to CPA on it and set a low CPA - smaller than the recommended cost per action. My actions are super simple trivial goals, but they're goals/funnels I track that give behaviors I want. I set this up, start my drive home from the office and get home to see that during my drive my budget was blown by nearly 200% and that all the traffic happened so quickly that my bounce rate was near 100% and response times were terrible...
Open a ticket with Google and they remind me that they say they can exceed your budget by 100%.. i guess in my mind i was still thinking 20%.. when did this change? Anyway.. they say don't worry about anything above the 100%.. which doesn't make me feel any better because in actuality the entire spend for the day was wasted spend because not only did CPA push me over my budget it blew down my web server, even hosting my cache on AWS and CDN.
Anyone else see this? is there anything I can do to try and stick with normal traffic patterns vs open the flood gates and beat the snot out of my servers?
BTW, i charged for all the clicks and there wasn't a single finished action.. does CPA do anything in this regard or do they only normalize the actions over longer periods then i would assume?