# dets If you want a disk-based version of `:ets`, then [dets](https://www.erlang.org/doc/apps/stdlib/dets.html) is your solution, at least if your state fits into a file of less than 2 GB. Moving the state to disk could free up some memory, but it will come with a significant performance decrease because all operations are now disk operations. ```elixir # Define a path for the file. If the file doesn't exist, dets will create it. # We have to convert the string to a charlist here, because that's what :dets expects. dets_file_path = String.to_charlist("./state.dets") # Open a new file {:ok, _pid} = :dets.open_file(:state, file: dets_file_path) # Write records to the file :dets.insert(:state, {:messi, %{age: 37, goals: 837}}) :dets.insert(:state, {:ronaldo, %{age: 39, goals: 900}}) # Look up a value :dets.lookup(:state, :messi) |> IO.inspect(label: 1) # Update a value by overwriting it :dets.insert(:state, {:messi, %{age: 37, goals: 838}}) :dets.lookup(:state, :messi) |> IO.inspect(label: 2) # Delete a record :dets.delete(:state, :messi) :dets.lookup(:state, :messi) |> IO.inspect(label: 3) # Flush the changes to disk. A file is auto-flushed every 3 minutes by default. # You can change this interval with the `auto_save: 1_000` option in `:dets.open_file/2` :dets.sync(:state) # Close the file. Don't forget this, otherwise your file isn't closed properly # and needs to be repaired the next time you open it, which might take a while. # # If you open the file from a process and the process terminates, this will be # called automatically. :dets.close(:state) ``` <!-- livebook:{"output":true} --> ``` 1: [messi: %{age: 37, goals: 837}] 2: [messi: %{age: 37, goals: 838}] 3: [] ```