Custom Record syncing with extternal systems

Background: My companies current public facing website is a .NET based site, which include a 'customer area', allowing customers to log in and see secured content. The authentication and authorization system uses NetSuite contacts and custom record types.

Basically we use 3 record types: contact (native), communities (custom) and communities_members (custom). The 'communities' records can be likened to groups, and different areas of our website are secured by different groups (i.e. you must be a member of a specific group to see certain content). The "communities_members' record contains: contact_id, community_id and membership_expiration. When a customer comes to our site and is authenticated (does a contact exist for their email address, does their contact record "communities_password" match the one entered), I then go to the "communities_members" records and retrieve all the records that match the logged in contact_id.