We know that indexes are necessary for query performance but comes with overhead during DML operations. Usually, the overhead is worth the performance gain we get out of them.
What I needed was to find and consider for removal indexes that incur heavy maintenance overhead, but are only lightly used for queries or enforcing constraints.
Here is an a version of query to find unused or lesser used indexes. It looks for non-unique indexes with large number of DMLs with ratio of writes vs reads is relatively high (I am using 10 but at this point its an arbitrary starting point).
AS (SELECT Db_name(iu.database_id) db_name,
Object_name(iu.object_id, iu.database_id) object_name,
Sum(iu.user_seeks) + Sum(iu.user_scans)
+ Sum(iu.user_lookups) total_user_reads,
FROM sys.dm_db_index_usage_stats iu
INNER JOIN sys.indexes i ON i.object_id = iu.object_id
AND i.index_id = iu.index_id
WHERE iu.database_id = Db_id()
AND i.index_id > 0
AND i.is_unique = 0
GROUP BY iu.database_id,
total_user_writes / total_user_reads write_to_read_ratio
WHERE 1 = 1
AND total_user_writes > 1000000
AND total_user_reads < 1000
AND ( total_user_writes / NULLIF(total_user_reads,0) > 10
OR total_user_writes / total_user_reads IS NULL )
ORDER BY write_to_read_ratio DESC
Please make sure to test before actually deleting any index.