To add to your comment, "I don't know" is a critical phrase, and so is following it with "help me understand the technical issues at play here" -- technical people generally love teaching someone who is curious, respectful, and has asked them to help guide a decision that is at least in part technical.
This works especially well when they can see you making a sincere effort to understand, by paraphrasing and repeating back what they've explained to you: "So what you're saying is that this component works like such and such, and one weakness of the approach is xyz? Am I understanding right?"
Also involving them in the business issues at play can help - "I hear you saying this approach will be more robust in the long run, and what you say makes a lot of sense to me. I'm struggling to balance this against business issues of the expected lifetime of this feature and our target ship date. If we are in a situation where we don't expect to use this feature for long and we have ship date pressure, what are your thoughts on the approach that is less robust in the long run?"
Doing the above helps keep people from thinking you're a poser who refuses to understand the issues, and also helps technical people from becoming grumpy about what may look like idiotic decisions that are in fact driven by a business issue that nobody told them about or included them on.
This works especially well when they can see you making a sincere effort to understand, by paraphrasing and repeating back what they've explained to you: "So what you're saying is that this component works like such and such, and one weakness of the approach is xyz? Am I understanding right?"
Also involving them in the business issues at play can help - "I hear you saying this approach will be more robust in the long run, and what you say makes a lot of sense to me. I'm struggling to balance this against business issues of the expected lifetime of this feature and our target ship date. If we are in a situation where we don't expect to use this feature for long and we have ship date pressure, what are your thoughts on the approach that is less robust in the long run?"
Doing the above helps keep people from thinking you're a poser who refuses to understand the issues, and also helps technical people from becoming grumpy about what may look like idiotic decisions that are in fact driven by a business issue that nobody told them about or included them on.