First checkpoint pickup of a large disaggregated catalog creates a local file per table. {}wt_config_collapse _rescans the file.meta default for every key, and _wt_config_tiered_strip merges the result again. On a release build, pickup of 10k tables was about 3.3s, most of that in file create. MongoDB's 2s election timeout fires on that. 

A prototype was implemented in config-overlay-file-create (2b5fee3792). It walks the defaults once, looks each key up only in the create config, and skips the tiered strip when the result has no tiered_storage key. Retesting with the prototype, the same 10k release run dropped from about 3.5s to about 1.0s.