Store the keys required by .NET Data Protection library in your PostgreSQL databae.
How to configure:
using DataProtection.PostgreSQL;
builder.Services.AddDataProtection().ProtectKeysWithCertificate(X509Repository.GetCertificate(connectionString));
builder.Services.Configure<KeyManagementOptions>(options => options.XmlRepository = new DataProtection.PostgreSQL.DataProtectionRepository(connectionString));
Available on Nuget as PPioli.DataProtection.PostgreSQL