Composability is the ability of components within a system to be reliably retrieved and recombined into larger assemblages. In the context of decentralized finance (DeFi), composability is a quality of the Ethereum ecosystem and is deemed crucial to the interoperability of crypto-finance protocols such as UniSwap.
'Atomic', in this context, means that any command executed across multiple components will execute as a unitary command that either wholly succeeds or fails.
Atomic composability [ /əˈtɑmɪk kəmˌpoʊzəˈbɪlɪti/ ] is an impediment for DeFi scaling solutions that employ sharding because of the communication between shards needed to maintain a global network state. Cerberus, Radix’s consensus mechanism, overcomes this by employing a deterministic, hash-indexed shardspace and by enabling shards to temporarily ‘braid’ the components (’substates’) of a transaction together.
Research by RDX Works has found that 69% of all Ethereum transactions utilize some degree of atomic composability.