The wmcs-wikireplica-dns script, when creating the CNAMEs for individual wikis, uses ensure_recordset which fetches details for an individual recordset from Designate and compares it to the live data, which is then repeated ~4,000 times for all the other records. Instead the script should fetch all the records in a given zone at once (which you can do with a single Designate call), and then figure out the required changes in the script.