This referendum is meant for enabling async-backing on polkadot, more information about what is async backing and what this parameter changes will do can be found here [async backing](https://wiki.polkadot.network/docs/learn-async-backing)

All async backing logic will be enabled with polkadot runtime upgrade [1.2.0](https://polkadot.subsquare.io/referenda/648), but in sync mode, parachains can produce block only at 12s rate.

After this referendum parachains can decide to produce blocks at 6s rate, by following this guide https://wiki.polkadot.network/docs/maintain-guides-async-backing, but that is not mandatory, they will still run at 12s rate without any changes needed on their side.

Whitelisted by: https://collectives.subsquare.io/fellowship/referenda/102.

## Testing done

Async backing has been running on Rococo since December 2023 and on Westend since February 2024 with all system parachains migrated to produce blocks at 6s rate and on kusama after https://kusama.subsquare.io/referenda/374

Our final checklist enablement can be found here: https://github.com/paritytech/polkadot-sdk/issues/3226

## Dependencies

- Async backing runtime APIs come in polkadot runtime v1.2, which will get enacted with: https://polkadot.subsquare.io/referenda/648, this referendum needs to be enacted after that.

## Known issues

No critical issues are known at this moment, however  to make the transition smooth all validators need to be upgraded to a version higher that *v1.8*. There are still around 3-5% validators in the active set that are not upgraded, so when it is their turn to back they won't back anything, and if 3 out of 5 nodes are in the same backing group the group won't be  able to back the candidates it is assigned to. **Action** Un-upgraded validators please upgrade to something higher than 1.8 node version.



See [`Pallet::dispatch_whitelisted_call_with_preimage`].

- **Problem Statement:** Implementing async backing on Polkadot to allow parachains to produce blocks at a faster rate.
- **Significance:** Enabling async backing can potentially enhance the efficiency and performance of the Polkadot network.
- **Proposed Solution:** Enabling async backing logic with the Polkadot runtime upgrade 1.2.0, allowing parachains to produce blocks at a 6s rate.
- **Expected Outcomes:** Improved network performance, smoother transitions for validators, and enhanced block production capabilities for parachains.

#688 Enable async backing on polkadot