Count Performance optimisation - performance

Question

I got 2 versions of basically the same code. (See below) Version 1 is running at 2 seconds, version 2 is running at .5 - .6 seconds. There are 10 million rows currently from where I am selecting from, but this number goes up pretty fast. I would like to go even lower if possible. The problem is that I use Version 2, and I need to call that 30 times (different statuses, different usernames, etc), the final number is still going to be too big for what I need. Is there a 3rd version I could use instead? Or is there any other way I could make this to be even faster? Or the only thing that I could do is play with indexes.
Basically all these counts would be displayed in the most visited screen in a web application, and 30 * .5 seconds sounds a bit too much when 1000 users are using the system in the same time.
Version 1
declare #a1 datetime; set #a1 = GETDATE()
declare #int1 INT,#int2 INT,#int3 INT,#int4 INT,#int5 INT,#int6 INT,#int7 INT,#int8 INT
select #int1 = COUNT(Id) from ToDos where StatusId = 1 and stringUserId = 'a'
select #int2 = COUNT(Id) from ToDos where StatusId = 1 and stringUserId = 'b'
select #int3 = COUNT(Id) from ToDos where StatusId = 1 and stringUserId = 'c'
select #int4 = COUNT(Id) from ToDos where StatusId = 1 and stringUserId = 'd'
select #int5 = COUNT(Id) from ToDos where StatusId = 1 and stringUserId = 'e'
select #int6 = COUNT(Id) from ToDos where StatusId = 1 and stringUserId = 'f'
select #int7 = COUNT(Id) from ToDos where StatusId = 1 and stringUserId = 'g'
select #int8 = COUNT(Id) from ToDos where StatusId = 1 and stringUserId = 'h'
select #int1, #int2, #int3, #int4, #int5, #int6, #int7, #int8
SELECT DATEDIFF(MILLISECOND, #a1, GETDATE())
Version 2
declare #a1 datetime; set #a1 = GETDATE()
select stringUserId, count(stringUserId)
from ToDos
where StatusId = 1 and stringUserId in ('a','b','c','d','e','f','g','h')
group by stringUserId
order by COUNT(stringUserId) desc
SELECT DATEDIFF(MILLISECOND, #a1, GETDATE())

Answer 1

Try conditional count.
select
#int1 = COUNT(CASE WHEN stringUserId = 'a' THEN 1 END),
#int2 = COUNT(CASE WHEN stringUserId = 'b' THEN 1 END),
#int3 = COUNT(CASE WHEN stringUserId = 'c' THEN 1 END),
#int4 = COUNT(CASE WHEN stringUserId = 'd' THEN 1 END),
#int5 = COUNT(CASE WHEN stringUserId = 'e' THEN 1 END),
#int6 = COUNT(CASE WHEN stringUserId = 'f' THEN 1 END),
#int7 = COUNT(CASE WHEN stringUserId = 'g' THEN 1 END),
#int8 = COUNT(CASE WHEN stringUserId = 'h' THEN 1 END)
from ToDos
where StatusId = 1
FYI: I didnt include the ELSE part for CASE because for default will return NULL and COUNT doesnt count nulls

Answer 2

You could try:
select a.* from (select stringUserId, count(stringUserId) as IDCount
from ToDos
where StatusId = 1 and stringUserId in ('a','b','c','d','e','f','g','h')
group by stringUserId) a
order by a.IDCount desc
that eliminates the count function from the order by