Really struggling with team/engineer

Before switching teams, do you know if other engineers on the team feel the same way? If it's just you encountering this level of friction, your manager sees the world like this:

• E6 with longer tenure with more equity is doing things the way they always do. This has historically had impact for the team/company/org.
• You (new E5) comes in and doesn't work well with the E6.
• You complain to manager.
• E6 gets paid more and has longer tenure => bigger risk to the team/org to disrupt them.
• Therefore, your manager will bias towards the E6.

In order for your feedback to be received, you need to put more weight on your side of the scale. You would need an E5+ in your org with tenture to also vouch for you. If not, your manager won't take any action.

Coming from someone who's in the position your E6 is, the main thing that causes me to more aggressively shoot certain people down is if they don't follow the same principles as I do. I'd look to figure out the following:

• What does your E6 value when it comes to engineering?
• What patterns does the E6 display when it comes to reviewing artifacts (code, docs, etc.)?
• How does your E6 view the world around them?

Once you figure those out, try to see if you can proactively incorporate those learnings into your workflow. Download your E6 and work with/around their behaviors. It might help to have your manager mediate in case you don't feel like your E6 will respond well.

(A few other misc notes)

• It's plausible that you might be taking enough scope to risk their E6 standing. If you feel like the friction they're putting is often amounting to nothing, start documenting these occurances and if they amounted to some changes.
• One key piece of feedback I got growing towards a TL was that I needed to shoot people down more.

I am consistently putting in 16 hours days to try and keep up with their demands.

This doesn't sound good at all :/ Have you talked to the Staff Engineer directly? Are they aware that you're putting this much effort in, and you have concerns about how they're giving feedback?

If you feel they are not receptive to your concerns, and they're deliberately trying to put you down, that is cause for concern, and you should absolutely talk to your manager or switch teams.

But you should talk to them using the tactics from Handling "Awkward" Conversations: Resolving Disagreements

It's important in this situation to have empathy and follow one of Meta's mantras: "Assume good intent".

E6s are incredibly busy, stressed out, and overwhelmed. This is going to get even worse given the sharply negative direction Meta's culture has gone down recently. It's not likely that this engineer is purposefully out to get you as that's not in their best incentive to do that. E6s largely achieve impact by delegating through their E5s.

As Jonathan mentioned, think of ways you can improve the relationship. It's not a matter of who's right or wrong on what here. It's a matter of finding a way that you 2 can synergize better together, and the onus is frankly on you as you're both new and less senior than this person (i.e. you have far less leverage).

I have been the stressed out tech lead many times before shooting people down (often newbies like yourself), including at Meta. It's a hard job, and there were many times where I didn't communicate in the most polite way or execute in the smoothest fashion which I regret as someone who genuinely tries to be a nice person. However, looking back on those scenarios, there was never a case where the person I shot down couldn't have done a better job by creating more intricate planning documents, spending more time getting to know me and other gatekeepers, and communicating more proactively. You should look for those opportunities.

All that being said, definitely talk to your manager about this. It's their job to resolve these interpersonal disputes, and 16 hour days aren't healthy. It's in their best interest to make sure you don't burn out.

Is it too early to switch teams? How quickly can this process occur?

Team switches generally require 1+ years on your current team with sustained "Meets All" or higher ratings. This means that it will be very hard for you to switch, especially given how Meta is now. However, it can be done in an emergency. You can try this if it's been over a month, and you and your manager still aren't able to solve this problem.

Here's a similar thread, which I highly recommend: "As a MLE, how should I communicate with a difficult backend engineering lead?"