The oldest trade in the book
Cash & carry is the classic basis trade, ported to crypto: buy the asset on the spot market and simultaneously short an equal amount via the perpetual on the same exchange. The two legs cancel each other's price risk — if the coin doubles, the spot leg gains what the short loses. What remains is income.
The income has two sources. The entry basis — perps usually trade slightly above spot, so you sell high (perp) and buy low (spot), locking that gap in at entry. And funding — perpetual funding rates are positive most of the time, meaning longs pay shorts. Your short collects that payment every settlement, for as long as the position is open.
Unlike two-leg spread arbitrage, cash & carry does not cycle — it holds. You build the position once and let funding accrue for days or weeks, unwinding when the carry stops paying. It is the slow, steady counterpart to funding rate arbitrage on two perps.
Basis convergence
Spot and perp converge by expiry — the closing gap is the profit
- Entry basis: the edge you lock in
- Perp drifts down toward spot
- Gap → 0 at expiry = captured profit
Basis, open and close spread
basis % = (perp − spot) ÷ perp- basis
- Positive basis at entry is profit you lock the moment both legs fill. It is realized, not hoped for.
Basis is the spot-vs-perp price gap, measured in percent: (perp − spot) / perp. Positive basis at entry is profit you lock the moment both legs fill — it is realized, not hoped for.
Two live numbers frame every decision. Open spread — (perp bid − spot ask) / spot ask — is what you would earn entering right now, before any funding. Close spread — (perp ask − spot bid) / spot bid — is what unwinding right now would cost. Both are shown on the position card in real time.
The profitability equation is honest and simple: entry basis + accumulated funding must beat fees on both legs plus the unwind cost. A tight entry basis is fine if funding is rich; a fat basis buys you margin for error.
How Arbitron builds the position
You set a target quantity and a chunk size, and the engine accumulates the position in chunk-sized pieces — buying spot and shorting the perp in matched sub-orders. Smaller chunks smooth execution and reduce market impact but pay more per-order fees; larger chunks are cheaper and faster but concentrate timing risk.
Two thresholds automate the timing. Desired basis is the minimum spot-vs-perp gap required before the engine fills the next chunk — it will not chase a poor entry. Move delta is the basis drop that triggers unwinding: when the live basis falls that far below your entry, the engine starts closing both legs to lock in the result.
The anatomy of carry PnL
net = realized + funding − fees- realized
- Realized PnL books at fill time: entry basis × filled quantity, minus the fees both legs paid. This is the locked-in part — it does not change afterwards.
- funding
- Funding total accumulates with every settlement on the perp short. This is the carry itself, and over a multi-week hold it routinely outgrows the entry basis. The card shows the current rate and a countdown to the next payment.
Net PnL = realized + funding − fees. If net is negative, the basis was too tight or funding underdelivered — the breakdown on the card shows exactly which.
Risks and requirements
Cash & carry is a Pro-tier feature and needs a venue that lists both spot and perpetual markets for the coin — that covers most supported CEXes, while perp-only venues (BloFin, Hyperliquid, Aster, Lighter) cannot host a carry.
Funding can flip negative
The main economic risk is funding flipping negative: in sustained bearish stretches shorts pay longs, and the carry bleeds instead of earning. Funding history in the drilldown shows how often a symbol has flipped historically; when the carry dies, unwinding is the position's natural end — not a failure.
Operational discipline
Operationally: keep perp leverage low — 1× is the most conservative carry setup; higher leverage frees capital but pulls the liquidation price closer to the market. Watch for leg imbalance (spot and perp quantities should match; a gap means a partial fill the engine is resolving), and remember the spot leg ties up full notional in capital — the carry result is based on unleveraged spot capital.