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Google Cloud Certified Professional Data Engineer · Google Cloud
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I need to save the hashes in a database. "A" is incorrect because: If the system doesn't already generate a GUID at the source, assigning one after it arrives in the cloud is pointless: two identical transmissions of the same data would receive two different GUIDs, making it impossible to detect the duplicate. "B" is incorrect because it doesn't state that the hash is saved or that the data is already in a database, so I would have to perform a massive check, which is unsustainable.
Why not the others: A. GUIDs: You can only assign GUIDs if the source system supports it. Here, the system retransmits without changing the payload, so GUIDs won't help unless added upstream. B. Compute hash and compare with all historical data: This is inefficient because you'd need to scan all previous entries every time. C. Store each data entry as the primary key: Payloads can be large and variable, making them unsuitable as primary keys. Also, indexing on large text fields is costly.
Option D correctly specifies that the hash value must be stored in a database table (or a high-speed key/value store like Redis/Memcached) with an index applied to it. This allows the ingestion service to perform a single, fast primary key lookup using the hash.