Keeper incentives

A keeper is an independent operator running a bot that sends transactions the protocol needs sent. Solana has no scheduler and the program cannot call itself, so every action not initiated by a trader has to be initiated by somebody: an order that reaches its trigger price, an account below maintenance margin, a mark TWAP that has gone stale. The protocol's job is to make those transactions worth sending.

A filler is the keeper's role in a fill, and a liquidator is its role in a liquidation. The pay is different.

The filler reward

A flat bounty per fill would either exceed the fee collected on a small order or be too small to be worth racing for on a large one. So the protocol pays two legs at once and takes the lesser: one proportional to the fee, which keeps the payment bounded by what was collected, and one growing with the order's age, which makes the oldest unfilled order the most attractive one to fill.

$$f_{\text{keeper}} = \min\left(0.10 \cdot f_{\text{user}},\; 0.01 \cdot m \cdot t_{\text{order}}^{1/4}\right)$$

where $f_{\text{user}}$ is the taker fee paid on the fill, $m$ is the price-improvement multiplier below, and $t_{\text{order}}$ is the order's age in whole 400ms periods, floored at 1. The size leg is 10% of the taker fee; the time leg starts at $0.01.

The fourth root is a flat curve: an order that has waited a hundred times longer is worth only about three times as much, which spreads keeper attention across the book instead of concentrating it on the single oldest order.

How the two legs behave

At a 1x multiplier, the time leg alone runs as follows.

The size leg is 10% of the taker fee, so at the Regular tier's 4 bps it is 0.4 bps of notional. On a freshly placed order the two legs cross at roughly $250 of notional. Above that, and on any order that has waited at all, the time leg binds instead and the fill pays a couple of cents regardless of how large the order was.

A $2,000 order filling 4 seconds after placement pays a $0.80 taker fee, of which the keeper gets $0.0177. A $100,000 order filling 4 seconds after placement pays a much larger fee, and the keeper still gets $0.0177. Order size buys the keeper essentially nothing; order age is what pays.

The price-improvement multiplier

The time leg is scaled by how far inside a baseline the maker's price was. The baseline is the oracle 10 bps against the maker: a maker bid 10 bps below oracle, or a maker ask 10 bps above it, earns 1x. Every further 10 bps of improvement adds one, so a maker bid at the oracle is 2x and a bid 10 bps above it is 3x, clamped between 1x and 100x. The smaller-of-the-two rule still applies afterwards, so on a $2,000 order, whose size leg is $0.08, the multiplier stops mattering above about 4.5x at 4 seconds of age.

The flat cancel fee

Cancelling and triggering are not sized off a fee, because there is no fee. They pay a flat $0.01 for each of:

• an order past its expiry that the keeper expires
• a reduce-only order that no longer reduces anything
• a maker order cancelled because its limit price breached the oracle bands
• a conditional order the keeper triggers
• each non-reducing order cancelled on an under-margined account

The payment comes out of the order owner's own quote balance in that market, not out of a protocol pool, so cancelling somebody's stale orders is billed to them. It is also conditional on the keeper being able to hold a position in that market: with no free position slot the cancellation still happens, unpaid. See Guard rails.

Liquidation rewards

Liquidation pays a per-market rate rather than a formula, taken from the liquidatee alongside the insurance fund's and the protocol's own liquidation cuts. Read the liquidator fee on the market being liquidated in; the initialization default is zero, so a market pays a liquidator only if an admin set a rate. See Liquidations.

The mark TWAP crank requires a staked keeper

The mark TWAP crank refreshes a market's bid, ask and mark TWAPs from the current orderbook, which is what funding is sized against. It differs from everything above in two ways.

It pays nothing. There is no filler reward and no flat fee. The keepers that run it do so because they need the funding rate to be right.

It requires a $1,000 insurance fund stake. The crank estimates the orderbook from user accounts the caller supplies, and the resulting TWAPs feed funding and the auction bands on other people's triggered orders. See Insurance fund staking.

Three further conditions apply. The keeper must not have this operation paused, which the admin can set per keeper. Quotes are counted only if they have rested at least 9.6 seconds, and quotes further than 15% from the oracle are discarded. And if neither TWAP moved, the call requires at least 60 seconds since the last mark TWAP stamp.

What this means in practice

For a fill bot, the reward is a function of age, price improvement and the fee, in that order. Racing to fill the newest large order pays one cent; filling the oldest orders on the book pays several times that.

For a cancel or trigger bot, every action pays exactly $0.01, so the economics are about transaction cost and inclusion. An account with 32 stale orders is worth $0.32.

For the TWAP crank, it costs $1,000 of insurance fund stake with its unstaking cooldown and pays no direct revenue. The reason to run it is that funding on a market is only as good as the TWAP somebody keeps fresh.