Because the Key Results (KRs) of OKRs actually encompass KPIs, Google, like anyone else who uses OKRs, technically uses both.
Take a look at how toOKRs and KPIs:
- OKR: Stands for “Objectives and Key Results;” it is a goal-setting framework that creates alignment, clarity, and transparency by strategically organizing and tracking predetermined objectives and the Key Results (or the metrics) that show progress towards the objective.
- KPI: Stands for “Key Performance Indicator;” a metric that determines factors needed to achieve success in an organization
As you can see, both KRs and KPIs are measurements. Essentially, the KR narrows the focus of the broader KPI. So, the KPI is built into the OKR, and everyone who uses OKRs is therefore also simultaneously using KPIs.
This relationship is illustrated in the infographic below:
Source: please read the blog and answers on Quora, very interesting read.