TL;DR: A traditional programmatic exchange runs auctions. Buyers bid on impressions, prices are set by competition, and the record is an impression log that the buyer holds alone. Alkimi runs a different kind of market: bilateral negotiations between agents, prices agreed rather than won, and deal records held by both parties in shared state. The structural difference determines what transparency and accountability a buyer can actually achieve.

Programmatic advertising has used the word "exchange" since at least 2007, when real-time bidding became the dominant mechanism for display buying. The term is accurate for what an exchange does: it clears auctions. Buyers submit bids, a clearing mechanism selects a winner, an impression is served. The buy-side has a log of what they paid; the sell-side has a log of what was served. Neither holds a shared record of the agreed terms, because in an auction, terms are not agreed. A price is won.

Alkimi is not built on this mechanism. It is built on bilateral negotiation and shared deal records. Understanding the difference is not a matter of vocabulary; it is a matter of understanding what accountability is possible in each system.

How a programmatic exchange works

In a conventional programmatic exchange, the transaction sequence is:

The publisher's ad server detects a monetisable impression opportunity. It passes a bid request to the exchange, containing information about the impression: the site, the placement, the audience data, the floor price. The exchange distributes this bid request to eligible DSPs. Each DSP evaluates the request against its buyers' campaign parameters and submits a bid or passes. The exchange runs an auction, selects a winner, notifies the winning DSP, and the impression is served.

The buyer's record is a bid log: what they bid, whether they won, and at what clearing price. The publisher's record is an impression log: what was served, when, and at what CPM. Neither party holds a shared document that captures both sides of the transaction. Reconciliation between buy-side and sell-side numbers is a periodic exercise against separate records, and discrepancies of 10-15% are common and widely accepted.

How Alkimi works

In Alkimi, the transaction sequence begins with a mandate, not a bid request.

A buyer defines a media buying mandate: a structured document that specifies what the buy-side agent is authorised to do. The mandate contains audience parameters, CPM range, inventory requirements, format constraints, and approval thresholds. The agent operates within this mandate. It cannot agree to terms outside the parameters without triggering an escalation to the human buyer.

The buy-side agent, operating from this mandate, engages with a sell-side agent representing publisher inventory. The negotiation is bilateral: the buy-side agent proposes terms, the sell-side agent evaluates and responds, and the process continues until agreement is reached or a no-deal determination is made. When agreement is reached, both agents record the same deal document, the DealSheet, which captures the agreed price, inventory specification, parties, and mandate reference.

The buyer holds the DealSheet. The publisher holds the same DealSheet. Neither can modify it after execution. Post-campaign reconciliation is against the DealSheet, not against separate ad server logs.

What this changes for buyers

The practical differences for buyers fall into three areas.

Price setting. In an exchange, the buyer's agent wins or loses impressions at prices set by competition. In Alkimi, the buyer's agent agrees prices within a defined mandate range. The buyer knows in advance what CPM range the agent can commit to. The agent cannot exceed the mandate without escalation.

Record integrity. In an exchange, the buyer's impression log is their own record. They cannot independently verify the publisher's corresponding numbers without a reconciliation process that both parties have to agree to conduct. In Alkimi, both parties hold the same DealSheet from the point of execution.

Audit trail. In an exchange, the buyer can audit their own bidding behaviour but cannot audit the sell-side conditions that produced the clearing price. In Alkimi, the buyer can audit whether the agent acted within mandate by comparing the DealSheet terms against the mandate parameters. The audit trail is self-contained and does not require a second party's cooperation.

Where a programmatic exchange still has the edge

An exchange has coverage that a bilateral marketplace does not yet match. The programmatic open exchange reaches billions of impressions per day across hundreds of thousands of publishers. Alkimi's publisher-side coverage, while growing, is smaller.

For buyers with high reach requirements across many publishers and formats, open exchange remains the more practical route for a significant proportion of their buying. The question is not whether to use Alkimi instead of an exchange, but which environment each type of buying belongs in. Bilateral negotiation makes most sense for premium inventory, for deals where mandate governance is a requirement, and for buyers who need the deal record for financial or compliance purposes. Open exchange remains the appropriate route for scale and reach.

The two mechanisms are complementary, and most sophisticated buyers will run both.