Boosted proposal

Upwork calls it "your way to move your proposal to the top of a client's list by using extra Connects". Eligibility to boost depends on "how strong of a match you are for the job", and you can always submit without boosting. If eligible, you bid any number of Connects on top of the Connects the proposal itself requires, and a bid table shows what others are bidding.

The four highest bids get the four promoted slots. A proposal "will remain boosted until the client interacts with your proposal, opens it three times without further action, sees it five times without interaction, or you're outbid". The auction closes after seven days or at the client's first hire, whichever comes first. A proposal that loses is still delivered, below the four slots.

You pay what you bid, not the next bid down: in Upwork's example the four winners pay 35, 30, 25 and 20 Connects. The base Connects are charged at submission; the boost is charged at the end of the auction, and only if you are still in the top four or the client interacted with the proposal while it was boosted. Being knocked out of the top four before any interaction costs nothing. Upwork gives 10 Connects the first time a freelancer boosts and is charged, once; it also runs "placebo auctions" on a very small share of posts, where no Connects are taken.

How Upsight uses it. Upsight sizes a boost bid to the live auction when it sends, then records the outcome from the Connects history rather than from the "Boosted" badge, which is a bid position and not a result: see boost auction and Connects refund.