Millisecond timestamps in the trade journal change the kind of questions that can be asked

[Shadow Trader]

A journal with entry and exit times to the minute can answer questions about strategy. A journal with times to the millisecond can answer questions about execution.

How long did the order take to fill? Was the fill before or after the news timestamp? Did the stop trigger on the first tick through the level or several ticks later?

Most platforms record the data. Few traders export it. A script that pulls the history, calculates order-to-fill latency and logs it next to the pair and the spread takes an afternoon to write.

Once it exists, patterns appear that no chart review would find. Latency is worse at the top of the hour. The third trade in a burst always fills slowest. A particular pair is consistently slower than the others.

These are the details that explain why a strategy performs worse live than in testing, and they only show up when the clock resolution is fine enough.

Which execution details are worth logging, and which ones turned out to be a waste of storage?