A trading calculation "back to back" refers to a transaction where two parties agree to buy and sell a particular asset or product at the same time, with the same terms and conditions. In this type of transaction, the two parties agree on a price, and the trade is settled immediately.
On the other hand, "futures-backed" trading refers to transactions where parties agree to buy or sell a particular asset or product at a future date, but at a price that is agreed upon in the present. In this type of transaction, the price is determined by the current market conditions, and the trade is settled at a later date.
In terms of calculating trades, back-to-back trading is usually straightforward, as the terms of the trade are settled immediately. Futures-backed trading, however, requires more complex calculations, as the price of the asset may fluctuate between the time the trade is agreed upon and the time it is settled. Traders may use various pricing models, such as the Black-Scholes model, to determine the value of futures-backed trades and to minimize their risk.
Link to the excel sheet : ZHAW Example of coffee trading with and without a stock exchange