# How does cryptsy.com allocate trades for many orders with same price

How does cryptsy.com allocate trades for many orders with same price ?

Orders can come from one or many accounts, my question applies to both situations, but it's obviously more interesting how they are executed when orders come from multiple accounts from different people. For example, if I see order for 100 BTC and want to attach my order for 0.1 BTC to the same price tag, what are my chances of getting a deal ? Do I get a deal only after all 100BTC exchanged ?

Obvously my question applies to both types: buy and sell orders.

Do other exchanges have same order allocation schema as Cryptsy ? If not, what allocation schemas do they use ?

Examples of possible allocations that I can think of:

1) First Come First Serve - earliest order gets deal first

2) Last Come First Serve - latest order gets deal first

3) Proportional - deal amount is distributed between orders proportional to amount of these orders.

4) Minimal split - system picks closest amount to avoid splitting orders into many small fractions.

5) Small orders first, Large Last - close as many orders as possible to keep minimum number of open orders in the system.

6) Each account gets equal share from new deal regardless of order size or time

7) Random per account - equal probability for each participating account to get a deal

8) Random per order - gives incentive to make many smaller orders rather than one large order

• possible duplicate of How do buy and sell orders work? Mar 31, 2014 at 4:53
• No exchange could ever use #2, it'd give an unfair advantage to those entering at last minute - high frequency trading only, no humans allowed! Numbers 3, 7 and 8 would still favor last-minute traders, though less than #2. #4 or 6 seem to me the only ones to be fair appart from #1 Mar 31, 2014 at 18:35
• While I have done no research whatsoever to prove it, I am pretty sure that only FIFO, 1) is used. Everything else is way more complicated and/or easy to game.
– Murch
Apr 1, 2014 at 13:05