To achieve optimal cross-shard composability in Sui smart contracts without slowing things down due to shared object dependencies, you should design your dApp around Sui’s object-centric architecture. You can do this by keeping most objects as owned objects instead of shared ones, since owned objects allow independent parallel execution across shards. When shared objects are necessary, limit their use to critical coordination points and apply fine-grained data partitioning to split large shared states into smaller, shard-friendly segments. Using event-driven or callback mechanisms helps you connect actions across shards asynchronously, avoiding synchronous bottlenecks. Also, structure your Move modules to minimize read-write conflicts and apply transaction batching for multi-object interactions, ensuring better throughput across validators.