Laravel - Get the last entry of each UID type

This is easy enough to handle in MySQL:

SELECT t1.*
FROM yourTable t1
INNER JOIN
(
    SELECT UID, MAX(created_at) AS max_created_at
    FROM yourTable
    GROUP BY UID
) t2
    ON t1.UID        = t2.UID AND
       t1.created_at = t2.max_created_at;

Translating this over to Eloquent would be some work, but hopefully this gives you a good starting point.

Edit: You may want to use a LEFT JOIN if you expect that created_at could ever be NULL and that a given UID might only have null created values.

You can use a self join to pick latest row for each UID

select t.*
from yourTable t
left join yourTable t1 on t.uid = t1.uid
and t.created_at < t1.created_at 
where t1.uid is null

Using laravel's query builder it would be similar to

DB::table('yourTable as t')
    ->select('t.*')
    ->leftJoin('yourTable as t1', function ($join) {
        $join->on('t.uid','=','t1.uid')
             ->where('t.created_at', '<', 't1.created_at');
    })
    ->whereNull('t1.uid')
    ->get();

Laravel Eloquent select all rows with max created_at

Laravel Eloquent group by most recent record