We managed to get a Tesco's delivery last week, which was a challenge - the best we've been do so far is about one delivery every two weeks or so (from different supermarkets). But that basically means sitting online for hours hitting the refresh button to see if a slot becomes available.

Hunter-gathering in the twenty-first century...

A couple of hours after our delivery had arrived, I happened to look out the window and see another Tescos delivery being dropped off about two doors down. So not only dumb UX, but from a logistics perspective, poor design as well.

What would make far more sense to me, particularly in this time of lockdown (probably after as well), is you load up your basket with your shopping, then specify half day slots when you'll be at home. i.e. "here's the 30 things I want, and I can be home for delivery any time Monday to Sunday for the next two weeks". or "I can be home for delivery on Friday morning, Saturday morning, and all day Sunday". Periodically the supermarket runs an algorithm to find the optimal delivery for each order (and obviously you don't get charged if you don't get a delivery) -- perhaps with some prioritisation for those who've been waiting longer for their delivery slot.

There's nothing massively complicated about this as an algorithm - group addresses in the same street which have an intersecting time period. Then group addresses with close proximity (maybe half a mile or so). Then look for addresses slightly farther apart, but still close enough that delivery can be optimised (half a mile up to a couple of miles) - perhaps some of those can be grouped with one of the first two groups as well. Give each of these delivery groups a certain amount of points. You then rank the deliveries by their points, and by the age of the oldest order in the group -- ungrouped orders would just be ranked by their age -- and send out notifications to the confirmed orders. Discount delivery charges for grouped orders, and if there are any remaining slots available, open them up to adhoc deliveries with a slightly higher charge.

There's more complexity to take into account, of course - the number of delivery vans versus the number of deliveries per van, distance to the supermarket/depo, etc. But still, the result is likely an improved user experience for everyone, better for the environment and probably more cost effective for the supermarkets.