I'm going to give a quick overview of by FB interview experience. I'll post my guess on what rating I got for each on-site round.
Phone screen

1. Did intial technical phone screen. I didn't do well during that round as I was rushing too much and wasn't thoroughly discussing my solutions with the interviewer.
2. Took a second phone screen that went much better. I slowed down and planned out my solutions with the interviewer before implementing.

Virtual On-Site

1. Coding Round: I got two LC medium questions during this round. I would say both questions were on the harder side of medium. I felt like I didn't do so well during this round. I spent a bunch of time on the first question and I suspect I didn't get to the optimal solution. I got through the second question with some partial pseudocode as we were running low on time. [Rating: 1 - low confidence hire/no hire]
2. Coding Round: I got two LC medium questions. I felt a lot stronger in this coding round. On the second question I struggled a bit with getting some bug free code down, but I did get there. Then we discussed one other optimization for the second question which I hadn't implemented. [Rating: 2 - hire]
3. Behavioral Interview: I had a pleasant conversation with the interviewer. I was asked several question about past experiences and conflicts, which I was able to describe. Then at the end I did a small coding question. I felt very prepared for this round. [Rating: 2 - hire]
4. System Design: I felt I started off well with this question. I was able to give a high level design and started to dig into details. Towards the latter third of the round, I felt that the interviewer and I were going around in circles about one aspect of the problem. [Rating: 2 - hire (being an optimist here)]
5. System Design: This system design round was a little unusual. The interviewer constantly peppered me in questions and a lot of times I felt like all of the questions were derailing me from my overall thought flow. I didn't feel like I walked away with a nice fully put together design for the question. [Rating: 1 low confidence/no hire]

Overall
I wasn't happy with my overall performance. Just about every LC q was somewhat familiar, but I hadn't practiced them in a long time, so I didn't have the solutions cached in my brain. It's a little upsetting because I know I would do pretty well at Facebook. I definitely embrace a lot of their philosophy when it comes to moving fast, being a self-sufficient engineer, and operating under pressure.

Even though the title of the post says "Pending", I'm a fairly self-aware person, so I have a good sense that I will not be extended an offer. At this point I'm just waiting for my recruiter to deliver the bad news in the next few days.