Ask HN: Tracking banner impressions when doing media buys?

Hi All,

I'm about to start doing niche media buys and would love to serve and track the banners/creatives myself.

That way I know exactly how many impressions I'm getting as well as have the flexibility to swap out banners, etc.

What's the recommended way to do this? Host your own system or is there a good service that does this?

Thanks