What it is
Waterfall routing is the standard distribution method in performance marketing. Rather than sending a lead to one buyer, you offer it to an ordered list of buyers, highest priority first, until it sells or you run out of buyers.
The name comes from the way an unsold lead drops from one tier to the next.
How waterfall routing works
When a lead enters your system it goes to Tier 1 first, your premium buyers who pay the most. If a Tier 1 buyer accepts it, the lead is sold. If they reject it (wrong geography, cap reached, does not match their filters), the lead drops to Tier 2, and so on through as many tiers as you have set up.
Each tier can contain multiple buyers. Within a tier, you might use round-robin, weighted distribution, or best-bid logic to pick which buyer gets first look. Either way, the lead always starts at the top and works down without skipping a tier.
Tier 1, premium buyers
Highest payout, strictest filters
Tier 2, standard buyers
Moderate payout, broader filters
Tier 3, catch-all or multi-sell
Lower payout, accepts most leads
Why it matters
Mostly it comes down to revenue. Without waterfall routing you are either sending leads to a single buyer (leaving money on the table when they reject) or distributing randomly across buyers (selling premium leads at standard rates). A well set-up waterfall gives the buyer who pays most the first chance at each lead.
How much a tuned waterfall adds over a flat distribution depends on your buyers, their prices and how often they reject. Operators often report a meaningful lift in revenue per lead, and on volume even a small lift adds up.
Common configurations
Most setups use one of three patterns, and plenty of operators mix them inside a single campaign.
Exclusive waterfall
The lead sells once and stops. Tier 1 gets first refusal, then Tier 2, then Tier 3. Most common in regulated verticals like finance where leads must be exclusive.
Multi-sell waterfall
The lead keeps flowing even after a sale. You might sell exclusively in Tier 1, then multi-sell in Tier 3 to non-competing buyers. Popular in insurance and home services.
Hybrid with ping post
Some operators run ping post within Tier 1 to get real-time bids from premium buyers, then fall back to fixed-price tiers below. In Hawfinch there is no auction: ping post buyers sit in the same waterfall and are tried one at a time.
How it works in Hawfinch
In Hawfinch, each campaign has delivery groups, which are the tiers, run in priority order. Inside a group, buyers are tried by priority, round-robin or weighted order. If a buyer times out, errors or replies with anything other than HTTP 2xx, the lead moves to the next buyer. Each buyer link has its own timeout, 30 seconds by default, and can optionally retry on network errors, 5xx, 408 and 429 responses. Hawfinch does not run best-bid logic: a 2xx reply is a sale.
Routing runs in the background. The API answers your source straight away when the lead is accepted, so the supplier and the consumer never wait for buyers to respond.
Each group has a delivery count, which sets how many buyers in that group can take the lead. By default the next groups are still evaluated after a sale, so a lead can sell to several buyers. To make a lead exclusive, set the delivery count to one and add group filters such as already sold or sold to buyer. Caps are daily, weekly or monthly, per group and per buyer link, and reset at UK midnight. A capped buyer is skipped. You can also add an optional delay, in seconds, to a group. To see how leads are selling, Reports breaks results down by campaign, buyer, supplier, source and delivery status.