You must ingest high-volume stock price messages into a single large in-memory DB and ensure downstream services see the latest prices. Each message has symbol, price, timestamp. How should you configure the Pub/Sub subscription?

A pull subscription with exactly-once delivery ensures that each stock price message is processed by your in-memory database application exactly one time, preventing duplicate updates that could lead to incorrect price data. While ordering is not strictly required if your application processes updates based on the timestamp within the message, exactly-once delivery is crucial for data integrity. Push subscriptions are less suitable here because they require a publicly accessible endpoint and can be more complex to manage for high-volume, critical data ingestion. Turning off exactly-once delivery (in any subscription type) risks duplicate messages, which is unacceptable for financial data.