I'm looking to get promoted to E4 in the next cycle, but I'm worried as my impact contribution isn't very clear. I've done a lot of work, but due to churn within my org (which includes a recent re-org), a good amount of my code isn't truly in production yet. I've documented my work in Quips and tasks to show that I did it, but I'm wondering if a lack of shipped impact will hold back my PSC.
Impact is important for every level of promotion, but I'd say that it's less important for E3 --> E4 at Meta. Especially if it's due to factors outside your control, such as the churn you mentioned. What matters most is:
How do you feel you did on the above criteria, and how much can the people around you (peers, tech lead, manager) also comment on this to justify your opinion. That's what I'd focus on.