The main plot of this episode will be ignored in this review. The side plot with Chief O'Brien and Nog makes this, in my opinion, the best episode of Star Trek: DS9 ever. The throughout the entire episode you see Nog make back door deals and favors to grease all the right wheels to ultimately get the part that Chief O'Brien needs, all the while reassuring Chief that all he needs to do is "trust" the process as he is pulling his hair out over it.
Nog's methods in this episode is exactly how things happen in the military. The established supply processes are so bogged down with bureaucracy that almost nobody gets what they need when they need it, or if an item does arrive in time, it's the wrong part sent because a system code marked it as a "suitable substitute" an example of this would be like ordering a fuel pump for a specific vehicle, and receiving a fuel pump for a different vehicle that would work if used with an adapter part, that you also do not have and can not get. So how do you get what you need? You find who has what you need, see what they want, and work backwards with the promise of "if I get you what you want, you'll give me what I need?" Until you can immediately make good on it, then let the dominoes fall and watch everyone be happy. This is what Nog does, and he executes it exactly as it happens in real life. The US Army would have been crippled by its own red tape ages ago if it weren't for an entire grade of E-4s (known affectionately as the "specialist mafia") who work these deals to get the job done every day.
When people talk about the races in Star Trek and say that Ferengi were based on modern day humans, this is the episode I think about. Props to Philip Kim for writing what I consider to be the most relatable episode in Star Trek.