Difficulties defining relationship for archived data - sql-server

Question

In short; we need a cache, that cache has related entities. We also need to then store the expired items in a separate table for compliance and archival reasons.
Imagine the following four classes:
public abstract class Cache
{
public int Id { get; set; }
public Cache()
{
Entities = new HashSet<Entity>();
}
public ICollection<Entity> Entities { get; set; }
}
public class AvailableCache : Cache
{
}
public class ArchivedCache : Cache
{
}
public class Entity
{
public int Id { get; set; }
public int? CacheId { get; set; }
public AvailableCache { get; set; }
public ArchivedCache { get; set; }
}
Together with the following DbContext:
public partial class DbCacheContext : DbContext
{
public virtual DbSet<AvailableCache> { get; set; }
public virtual DbSet<ArchivedCache> { get; set; }
public virtual DbSet<Entity> Entities { get; set; }
protected override void OnModelCreatning(ModelBuilder modelBuilder)
{
modelBuilder.Entity<ArchivedCache>(p =>
{
p.Property(p => p.Id)
.ValueGeneratedOnAdd();
p.HasMany(p => p.Entities).WithOne(p => p.ArchivedCache).HasForeignKey(p => p.CacheId);
}
modelBuilder.Entity<AvailableCache>(p =>
{
p.HasMany(p => p.Entites).WithOne(p => p.AvailableCache).HasForeignkey(p => p.CacheId);
}
}
A recurring job populates the cache, checks for expired items and archives them. First attempt a column was added to ArchivedCache
public class ArchivedCache : Cache
{
public int OriginalId { get; set; }
}
This was then used as to save the original ID to define the relationship toward Entity. Then I tried to remove that, adding the ValueGeneratedOnAdd() and give it the same ID as AvailableCache.
The issue is that when trying to insert an Entity the foreign key constraint won't allow it since it doesn't exist in that table.
Since AvailableCache and ArchivedCache basically same object I would like to keep the relationship simple toward Entity.
Currently as I see it I have three options, I don't like any of them:
Define both IDs on Entity (I don't like this option because I don't want to clutter Entity with two ID:s that in the end point toward the same object, just in different tables/times)
Skip the ArchivedCache relationship and let the DBA worry about it since he was the one that specifically requested this.
I could remove the abstract class, resulting in one table with a discriminator but the DBA insisted on two tables.
But before I do either I wanted to check if there's perhaps something in EF Core that would allow this.