Scalable Multi-Domain Service Transactions via Hierarchical Conflict-Aware Scheduling and Digest-Based Batch Commit

Multi-domain service platforms increasingly require atomic workflows that span multiple autonomous domains with shared mutable states (e.g., blockchains, databases, and stateful microservices). Such settings face three practical challenges: delayed state visibility across domains, black-box internal scheduling inside each domain, and complex dependency cycles that span domains. To address these challenges, we propose a practical framework for multi-domain service transactions in deployments where participating domains accept ordered batches endorsed by a Byzantine fault-tolerant validator set (e.g., permissioned domains governed by a shared BFT group). First, we formalize the Optimal Cross-domain Serializable Schedule (OCS²) problem and prove its NP-hardness. Second, we introduce a unified transaction footprint model that integrates Account-based and UTXO-based semantics for universal conflict detection across heterogeneous domains. Third, we propose the Hierarchical Conflict-aware Scheduling (HCS) algorithm that transforms the NP-hard (OCS²) problem into parallelizable sub-problems through hierarchical decomposition. Finally, we design a digest-based batch commit protocol (HOBC) that shifts agreement from individual transactions to batch-level result digests. To handle delayed visibility and state drift between analysis and execution, the protocol validates execution-time preconditions and safely aborts transactions whose prerequisites are no longer satisfied, without compromising correctness. Our prototype evaluation shows improved concurrency efficiency under contention while preserving end-to-end correctness for cross-domain service transactions.