One file per employee with personal details, contract history, job changes, documents, training, reviews and leave balances. You decide per field and per role who can see what: a manager sees something different from HR, and a colleague only sees what you deliberately make available.
The biggest time saving is in self-service. Employees change their own address, request leave, check their balance, upload expense claims and download their documents, via the browser or the mobile app. That takes HR out of dozens of small processes a week as the go-between.