When all values of a JSON dynamic path within a single data part share the same type (e.g., all Int64), store that path as a plain typed column (1 .bin + 1 .cmrk2) instead of a full Dynamic column (5 substream pairs = 10 files). This eliminates the variant_discr, dynamic_structure, SharedVariant, and SharedVariant.size substreams that are redundant when type is homogeneous.
The JSON type stores each dynamic path using the Dynamic (Variant) type, which always produces 5 substream pairs per path:
payload.field.dynamic_structure.{bin,cmrk2} -- which type is this row