On my Uber Visa with Barclays alerts set, the transaction alert doesn't come until the transaction has posted, sometimes up to 24hrs after it has posted. The Visa alerts are emailed every time your card is swiped or authorized regardless of whether it eventually actually posts.
There are pros and cons to both approaches. The Barclays emails only alert you when something definitely posts to your account and gives you the final total. The Visa emails alert you every time your card is used but the total is preliminary only.
So for instance, you spend $100 at a restaurant and tips $20. Visa will email you right after the server swipes your card but will only show $100 since you haven't set the tip yet. There will be no update for the final authorized total including tip once that goes through. Barclays will alert you 2 days later but will show $120. The first is intended more as fraud alert while the second is more for you to keep track of spending.
