PVQ (formerly XCQ) – Completion Report & Retroactive Funding Request

Track: Polkadot Fellowship Treasury
Date: 12 Aug 2025
Proponent: 14DsLzVyTUTDMm2eP3czwPbH53KgqnQRp3CJJZS9GR7yxGDP
Beneficiary: 12zgSMDwF5xpzcksvEdDzcSFouFNroXGRffgnhogSk1kR7iS
Amount requested: 102,054 DOT (≈ $399,680 USD)

TL;DR

PVQ (PolkaVM Query), previously named XCQ, is now implemented with end-to-end demo. It standardizes cross-consensus (cross-chain) queries with a protocol, reference implementation, runtime components, SDK, docs, and a live demo. This request covers the remaining payment for the previously granted proposal (https://polkadot.subsquare.io/treasury/proposals/831). An upfront tranche of 49,075.43 DOT (USD 334,400) was received; this proposal requests a one-time payout of 102,054 DOT to settle the remainder.

What is PVQ

PVQ is a framework for querying data across chains. It is designed to integrate cleanly with PolkaVM and to operate alongside XCM or via runtime APIs and SDKs for off-chain clients. Goals:

Minimal, extension-based core for flexibility
Consistent query model across heterogeneous chains
Clean developer experience via SDKs and examples

Links (deliverables)

RFC: https://github.com/polkadot-fellows/RFCs/blob/main/text/0126-introduce-pvq.md
Main repo: https://github.com/open-web3-stack/PVQ
TypeScript/JavaScript SDK: https://github.com/open-web3-stack/pvq-sdk
End to end demo: https://open-web3-stack.github.io/pvq-sdk/
Status reports: https://forum.polkadot.network/t/cross-consensus-query-language-xcq/7583/24

Scope delivered

All milestones from the original XCQ proposal are complete:

Protocol and core design
Reference implementation in Rust (PolkaVM-based)
PVQ pallet and runtime library
TypeScript/JS SDK
End-to-end demo and developer documentation
Initial extension set covering common cross-chain data needs

Impact

PVQ removes fragmentation for builders who need accurate, verifiable cross-chain data:

On-chain use: staking pools that query Relay Chain rewards; automated coretime buyers; cross-chain treasury ops that need prices, fees, and slippage.
Off-chain use: wallet and bridge UX with correct fee computation; universal dApps that discover features and build extrinsics reliably.

Work summary and team

Effort: 68 weeks at 1.2 FTE (core delivery) + 4 weeks frontend engineering
Team: 1 full-time blockchain engineer; 1 CTO at 10%; 1 PM at 10%; 1 frontend engineer for 4 weeks
Reference rate used for planning: USD 220/hour

Funding request

Requested payout: 102,054 DOT to the beneficiary above.
Rationale:

Core: 68 weeks * 1.2 FTE * 40 h/week * 220 USD/h = 718,080 USD
JS SDK & Frontend Demo: 4 weeks * 40 h/week * 100 USD/h = 16,000 USD
Subtotal: 734,080 USD
Less upfront received: 734,080 - 334,400 = 399,680 USD
With DOT EMA7 Price: 3.916348 = 102,054 DOT

Next steps: PVQ in polkadot-sdk and system chains

We intend to integrate PVQ into polkadot-sdk and integrate it into system parachains and relaychains. Early discussion: https://github.com/paritytech/polkadot-sdk/issues/8251. We will submit a separate proposal for this integration.