Need guidance on partioning

Hello everyone,

I hope you are all doing well.

I am seeking guidance on how to implement partitioning in PostgreSQL.

We have a large table that currently does not have any partitioning, and we
have two requirements for removing old data from this table. We are looking
to create a new table with partitioning.

1. The first requirement is to delete all records from the table that are
older than 18 months. I believe we can achieve this by using range
partitioning on the timestamp column.

2. The second requirement is to remove data from the table when a user
leaves the organization. We have the account ID and user ID in the same
table.

Could someone please offer guidance on selecting the appropriate
partitioning method (range, sub-partition, or composite)?

Additionally, not all queries use the timestamp column in the WHERE
condition. Is it mandatory to use the partition key in the WHERE condition
to benefit from partitioning? Can we create a composite index that combines
the partition key column with other columns used in the WHERE clause? Would
this be beneficial?

Thank you.