Feature request: Option to require explicit expected version (disable ANY and exists)

[edge90]

Hi,

First, thanks for creating SierraDB. It’s a very promising project and I’m looking forward to working with it.

I have a feature request: an option to require strict optimistic concurrency for EAPPEND. This means disallowing EXPECTED_VERSION ANY, disallowing EXPECTED_VERSION exists and rejecting appends that omit EXPECTED_VERSION entirely.

Reason

In systems that rely on strict event-sourcing semantics, every append should use an explicit expected version tied to the decision the writer made. Allowing ANY or exists makes it possible for developers or services to bypass concurrency checks, which can lead to subtle issues in multi-writer scenarios (commands being applied based on stale state without any error).

It would be very helpful if the server could enforce this rule rather than relying only on client-side discipline.

Desired behavior

When this option is enabled:

• EAPPEND ... EXPECTED_VERSION ANY is rejected.

• EAPPEND ... EXPECTED_VERSION exists is rejected.

• EAPPEND without an EXPECTED_VERSION is rejected.

• Only the following are accepted:

  • EXPECTED_VERSION empty (for creating a new stream).
  • EXPECTED_VERSION <integer> (for appending to an existing stream).

This would make concurrency guarantees explicit and enforceable at the server level.

Thanks again for the project.

[tqwewe]

Hi thanks for opening this issue.

I definitely agree having a more strict configuration for this would be ideal. In fact, I'm wondering if this should be enabled by default.

The naming of this config could be something like:

[write]
strict_concurrency = true  # Require explicit version for all appends

Having this enabled by default would be the safest, but some of the existing tutorials would need updating, since they don't include the expected version argument, but that's an easy fix.