Performance evaluation is one of the oldest organizational processes. The first thought that pops up in our minds is likely a yearly event where two people meet and fill out a questionnaire about the previous year's accomplishments.
Thankfully, new models are surfacing. There is an emphasis on quarterly or even monthly conversations between managers and employees as part of the appraisal procedure. No numerical evaluations from the manager, open and honest dialogues with a primary focus on the future, leveraging the employee's talents to improve performance.
For example, a manager can meet with an employee every quarter to discuss their contribution to the previous quarter's objectives - what they've learned and how they've contributed to the team's OKRs. They can discuss the subsequent quarter's goals to ensure that expectations and priorities are aligned.
Most organizations will need to train their managers on how to structure such a conversation and what questions to ask; for example, the scoring of individual Key Results should never be discussed in these interviews, as doing so would undermine the concept of ambitious targets and the very purpose of introducing OKRs to the business.