So a guy is charged with tax accounting fraud for basically not putting some number into some entry in a spreadsheet when some external event happened, and instead putting that number into a different entry in the spreadsheet. You can't just say "you know how cars are complicated? Well so are spreadsheets. That's why this guy is guilty." Your analogy has to capture some legally-relevant dynamic of the system you are trying to explain.

Imagine your case depends on proving that only a guilty person would have failed to shard a particular database. It's not enough to just explain at the highest possible level the concept of splitting up a database. You gotta get the jury to understand it enough to know why you do it, and why it would be so out of the norm to not do it in a particular situation that the person must have had a nefarious motive.