To avoid creating duplicate contacts when migrating into Universal Containers, what methods can be used?

Creating a new text field for a hashed value as an External ID is an effective method to avoid creating duplicate contacts during migration. By hashing specific fields (such as email addresses or phone numbers) into a unique value, you can ensure that each contact is identified with a distinct hash. This hash can then serve as an External ID, which Salesforce uses to match existing records. If a record with the same hash already exists in the system, Salesforce will treat the new record as a duplicate, preventing the creation of unnecessary duplicates during the migration process.

Using a hashed value is beneficial because it allows for a consistent and unique identification method that does not rely on the exact values of the fields themselves, which may change or be formatted differently over time. Additionally, hashed fields are typically shorter than the original data, which helps in optimizing storage and retrieval.

Other options, such as creating an indexed formula field for a search key or a new formula field for a combination of name and address, may not provide the same level of uniqueness or efficiency in preventing duplicates. Indexed fields can improve search performance but do not inherently ensure that duplicates are avoided. Implementing a merge strategy post-migration can help clean up duplicates after the fact, but it is always more efficient to prevent them