Data storage over immutable and mutable data stages

A method comprising:

• receiving, by a processing node, a read request regarding a dataset;
• attempting, by the processing node, to fulfill the read request in relation to a mutable data stage, a sole copy of which is stored by shared memory accessible by the processing node and other processing nodes;
• in response to unsuccessfully fulfilling the read request in relation to the mutable data stage, fulfilling, by the processing node, the read request in relation to an immutable data stage, at least a partial local copy of which is stored by the processing node in local memory thereof;
• and
• returning, by the processing node, a response to the read request as has been fulfilled.

A non-transitory computer-readable data storage medium storing program code executable by a management node to:

• determine that an immutable data stage stored in shared memory accessible by the management node and each of a plurality of processing nodes and cached at least in a local memory of each processing node is to be updated with a mutable data stage solely stored within the shared memory;
• in response to determining that the immutable data stage is to be updated with the mutable data stage, freeze the mutable data stage as an intermediate data stage;
• process the intermediate data stage;
• update the immutable data stage stored in the shared memory with the processed intermediate data stage;
• and
• provide the updated immutable data stage to each processing node.