It is very interesting although I didn't really understand the 'security' part. The motivation seems to be twofold - some bad things have happened because of compromised npm packages and v8 happens to have a robust sandbox. This sounds like a solution looking for a vaguely defined problem. The illustrative example he gives is 'malicious linter'. Is malicious linter that important a threat?

In the example the linter itself is not malicious, but used to deliver a malicious program that can have unrestricted filesystem access. Not vague at all, see recent news on the ‘event-stream’ package being used to steal cryptocurrency wallets.

The 'vague' part is not that it doesn't happen - see the comment you are replying to.

> Access between V8 (unprivileged) and Rust (privileged) is only done via serialized messages defined in this flatbuffer.

Expect to see this in "n things I regret about deno"

Replying to Flatbuffers concerns:

You are right, we will try to get rid of it for some faster serialization mechanisms (after some huge internal refactor lands). See the talk I posted, Ryan mentioned about it near the end.

Can you explain why?

Every deno API function call goes through flatbuffer serialization + deserialization + more steps. Sounds like a lot of overhead.