Imposter syndrome hits at all levels too. I had it when starting my first SE role, and had it again when I moved to a more advanced role at another company. Many of the people you interact with when starting are comfortable with the tooling & stacks due to having historical context and knowledge. 1-on-1’s with you manager can help ensure you’re hitting the goals set for your onboarding, and over time as you become more comfortable the feeling fades.