A distributed computing environment is provided with a system and method for supporting rare copy-on-write data access. The system operates a data structure in a read only pattern suitable for serving a plurality of read requests with reduced overhead. The system, upon receiving a write request, creates a copy of data to execute the write request. The system defers writing the mutated data back to the read-only data structure. The system thus allows for multiple mutations to be made to the copy of the data using a read/write access pattern. After a number of read-only requests are received, the mutated data is written back to the read-only data structure. A monitor counts read and write requests in order to reduce overall read/write overhead and enhance performance of the distributed data grid.