1. The Exchange. Ability to send out bid requests to all bidders at each impression, and evaluate the bid responses quickly. Think of it as a large message hub where bid requests and responses are sent and received concurrently and continuously.

2. Compact bid request and response objects. There are a lot of bid requests and bid responses, so make sure these requests and responses are serialized in a very compact form for processing and transferring.

3. Filtering. Bidders won’t be happy if you send them 100M bid requests a day, if they are only interested in a small percent of them. Make sure there are some sorting filtering for bid requests.

4. Auction dynamics. How to set up auction dynamics, whether it’s 2nd price auction or price-winning distribution model? The auction dynamics must be simple for bidders to participate actively.

5. Creative approval. The relationship between advertisers and publishers are now managed by the ad exchange. So it’s ad exchange’s responsibility to approve creatives.

6. Inventory approval. Same as creative approval, it’s ad exchange’s responsibility to make sure impressions are brand safe.

7. Transparency. Make sure there are transparency between the exchange and the bidders. This includes any updates to the exchange feature, the pricing dynamics, and most importantly the bid request and response formats.

Overall RTB is huge step forward for online media buying, but building a good ad exchange requires not just good technology but also a robust process for maintaining a partnership relationship between the bidders and the exchange.

- charles