Order and position management in (semi-)automated trading system

External question — Quantitative Finance Stack Exchange Author: Konsta Original post: https://quant.stackexchange.com/questions/4344 License: CC BY-SA 3.0 — https://creativecommons.org/licenses/by-sa/3.0/ Adaptation: HTML converted to plain text; contact email addresses removed. A simple and lazy approach to implementing an order and position management (OPM) component in a (semi-)automated trading system: leave most OPM to counter party (broker/exchange). Even then funds and positions need to be checked once orders are supposed to be dispatched. Else it is unkown whether one has funds or already the intended position in a symbol. Certainly such requests/responses do not fit ultra high frequency trading (uhft), or are optimistic approaches with respect to order execution used? If not, what is the uhft OPM [software] design approach? Is the lazy approach good enough for lower frequency trading? Or are other [software] design patterns favorable? Which and why? Although the title What approaches are there to order handling in automated trading? is promising, answers were geared towards a specific difficulty. The references for developing an automated trading system do not discuss OPM in detail. A refined OPM component should reflect almost all account details (funds, transmitted orders, fills) reliably. I believe software design patterns of banking/exchange platforms should apply. References for reliable messaging/databases accessible to the non-expert developer would be nice.