Core answer
Start here. This is the direct spoken answer to practice first.
Why this question matters
Brokers are not file stores. Large payloads create cost, latency, and reliability problems, especially when messages are retried or dead-lettered.
I would avoid putting large files or huge JSON bodies directly in the message. Instead, I would store the large payload in durable storage and put a reference in the message, such as a storage key, version, checksum, and content metadata. The worker uses the reference to fetch the payload when processing. This is often called the claim-check pattern.