Optimizing Max Value query - sql

Question

I wanted to ask for advice on how I could optimize my query? I hope to make it run faster as I feel it takes away from the UX with the speed.
My program collects data every hour and I want to optimize my query which takes the latest data and creates the top 100 people for a specific event,
SELECT a.user_id as user, nickname, value, s.created_on
FROM stats s,accounts a
WHERE a.user_id = s.user_id AND event_id = 1 AND s.created_on in
(SELECT created_on FROM stats WHERE created_on >= NOW() - '1 hour'::INTERVAL)
ORDER BY value desc
LIMIT 100
The query I have returns the top 100 from the last hour for event_id = 1 but I wish to optimize it and I believe the subquery is the root cause of the problem. I've tried other queries but they end up with either duplicates or the result is not from the latest dataset
Thank you
EDIT::
The table account contains [user_id, nickname]
the stats table contains [user_id, event_id, value, created_on]

Answer 1

NOW() - '1 hour'::INTERVAL in not MySQL syntax; perhaps you meant NOW() - INTERVAL 1 HOUR?
IN ( SELECT ... ) optimizes very poorly.
Not knowing the relationship between accounts and stats (1:1, 1:many, etc), I can only guess at what might work:
SELECT a.user_id as user, nickname, value, s.created_on
FROM stats s,accounts a
WHERE a.user_id = s.user_id
AND event_id = 1
AND s.created_on >= NOW() - INTERVAL 1 HOUR)
ORDER BY value desc
LIMIT 100
INDEX(event_id, value) -- if they are both in `a`
INDEX(user_id, created_on)
or...
SELECT user_id as user, nickname, value,
( SELECT MAX(created_on) FROM stats
WHERE user_id = a.user_id ) AS created_on
FROM accounts
AND event_id = 1
AND EXISTS
( SELECT *
FROM stats
WHERE created_on >= NOW() - INTERVAL 1 HOUR
AND user_id = a.user_id
)
ORDER BY value desc
LIMIT 100
INDEX(user_id, created_on)
INDEX(event_id, value)
Please provide
SHOW CREATE TABLE for each table
EXPLAIN SELECT ...; for any reasonable candidates