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Resource record TTL is inheritable and synchronized with Route53. Therefore, any changes to the TTL value directly on the record or in the inheritance chain will be *synced to Route53. The serial number of the SOA record is not a syncable field. Any changes made to the SN of the SOA record, whether it be due to an edit change or a natural increment due to zone related changes, are not synchronized to Route53.
*Currently, this applies to Route53 public zones only.