Most efficient way to load/create Raycast targets (e.g. Colliders)?

This thread is the non-DOTS version of Most efficient way to load/create Raycast targets (e.g. Colliders) with DOTS?

What is the most efficient way to load/create/serialize/deserialize a (Mesh)Collider?

The goal is to be able to as fast as possible load a mesh from disk, raycast against it to determine:

• Vector3 hitpoint
• int triangle index

and then unload it again.

My current plan is to use MessagePack-CSharp as fast deserializer, but letting Unity create the MeshCollider is a huge bottleneck and I have not found a way to (de)serialize a MeshCollider more efficient.