class ActiveSupport::Cache::Store

def exist?(name, options = nil)

Options are passed to the underlying cache implementation.

Returns +true+ if the cache contains an entry for the given key. 
def exist?(name, options = nil)
  options = merged_options(options)
  instrument(:exist?, name) do |payload|
    entry = read_entry(normalize_key(name, options), **options, event: payload)
    (entry && !entry.expired? && !entry.mismatched?(normalize_version(name, options))) || false
  end
end