Spot crypto: spreads, depth, and execution

What spot exposure means

A spot purchase exchanges one asset for another at the agreed terms rather than entering a contract whose payoff is calculated later. Buying a token with cash does not necessarily give immediate control of a private wallet: a centralized venue may record a customer balance internally until withdrawal. That distinction matters when comparing market exposure with custody exposure. The token price could stay unchanged while access to the venue becomes a problem.

Crypto markets are fragmented. The same token may trade against dollars, other national currencies, or several stablecoins across different venues. Quotes can differ because of fees, transfer delays, capital restrictions, counterparty concerns, or temporary imbalances. A price difference is not automatically a realizable arbitrage profit. Moving funds between venues may take longer than the opportunity lasts.

Read the order book as a ladder

An order book lists resting buying and selling interest. The best bid is the highest displayed buying price; the best ask is the lowest displayed selling price. Their difference is the spread. Depth describes quantities available at successive prices. A large market order can consume the first level and continue through less favorable levels, producing an average execution price worse than the initial quote.

Visible depth is not a promise. Orders can be canceled, hidden liquidity may exist, and other traders can act before your order arrives. A market order prioritizes execution, not a fixed price. A limit order sets a price constraint, but may remain unfilled or fill only partly. Choosing an order type trades one uncertainty for another rather than eliminating uncertainty.

Costs arrive in several places

Trading fees, spreads, and market impact are different costs. A platform may advertise a low transaction fee while the quoted conversion price includes a meaningful spread. Deposits, withdrawals, and network transfers can add further expenses. A fee charged in the token itself changes the quantity remaining; a fee charged in cash changes the cash outlay. Keep the units explicit.

Compare a hypothetical transaction using an all-in cash-flow table. Record the cash paid, tokens received, cash proceeds from a sale, and every fee. Avoid counting the spread twice if actual buy and sell prices already include it. For frequent strategies, tiny per-trade costs accumulate, and a backtest that assumes frictionless execution can look much better than the process it supposedly represents.

Liquidity is conditional

A market can look deep during an ordinary afternoon and become thin during a sudden announcement. A reported daily volume figure does not tell you how much can execute now near the current price. Volume may be concentrated on another pair or venue. Small tokens can also face manipulation or abrupt delisting, making the exit more difficult precisely when many holders want it.

A useful paper exercise is to calculate the average fill for three different order sizes using a frozen order-book snapshot, then repeat after removing half the depth. This is not a forecast. It teaches why position size and liquidity belong in the same conversation. For any real product, execution rules, outage policies, and legal protections must be checked in the relevant jurisdiction rather than inferred from an attractive interface.

A cheaper fee can hide a more expensive trade

Compare two fictional quotes for buying 100 tokens. Venue A offers an average executable price of $10.00 and charges 0.30%, for a total of $1,003. Venue B advertises a 0.10% fee, but the available depth gives an average price of $10.04: $1,004 plus $1.004 in fees, or $1,005.004. The lower percentage fee did not produce the lower cash outlay. This comparison assumes both orders fill exactly as quoted and ignores transfers.

Next, add the cost of the exit you actually need. If one purchase must be withdrawn, a network or withdrawal charge belongs in that route’s cost. If the alternative leaves you with a stablecoin rather than cash, include the later conversion and its uncertainties rather than treating the stablecoin balance as money already in your bank. Keep each cost attached to a specific step; otherwise it is easy to omit a charge or count the same spread twice.

A useful comparison sheet has columns for intended quantity, executable average price, trading fee, withdrawal quantity, exit currency and total cost. Freeze the time of the quotes. A morning quote from one venue and an evening quote from another do not establish a fee advantage when the market has moved between them.

Partial fills change the decision

Consider a limit order to buy 100 units at no more than $10. Only 40 units trade before the price rises. You now have a position of 40 units and an unfilled instruction for 60, not a completed purchase at an average of $10 for all 100. A limit price constrains eligible executions; it does not supply the missing sellers. An order book records available quantities as well as prices. Coinbase’s order-book explanation covers that distinction.

For paper practice, decide beforehand whether a partial fill is acceptable and when the remaining order should expire. Record any cancellation and its confirmation; do not assume that pressing a button and having an order canceled are the same event. If the unfilled balance later executes, it changes your holdings even if you have stopped watching the screen. Evaluating execution therefore means reconciling orders, fills and balances, rather than checking only the last traded price.