# Pinning code

Pinning a code ID adds it to validators' cach. In effect, this removes startup fees associated with invoking contracts that use that code ID.

# Querying pinned code

You can see which contracts are currently pinned with

rebusd query wasm pinned

This will return a list of code IDs that have been pinned:

rebusd query wasm pinned --node $NODE         
code_ids: []
  next_key: null
  total: "0"

# Pinning and unpinning code through governance

Frequently-used contracts can be pinned in the mainnet by governance proposal. To do so, create a PinCodesProposal

The content of the proposal looks like this:

 "title":"Pin Wasm Codes",
 "description":"Pin cw20, cw721 wasm codes",
 "code_ids": [1, 5]

You can now build this into a SubmitProposal message:

{"body":{"messages":[{"@type":"/cosmos.gov.v1beta1.MsgSubmitProposal","content":{"@type":"/cosmwasm.wasm.v1.PinCodesProposal","title":"Pin Wasm Codes","description":"Pin cw20, cw721 wasm codes","code_ids": [1, 5]},"initial_deposit":[],"proposer":"rebus17p23vp5c80qmztss8aj9myrt8dc69zel0urmk5"}],"memo":"","timeout_height":"0","extension_options":[],"non_critical_extension_options":[]},"auth_info":{"signer_infos":[],"fee":{"amount":[{"denom":"urebusx","amount":"5000"}],"gas_limit":"200000","payer":"","granter":""}},"signatures":[]}
  "title": "Pin cw20 contract",
  "description": "Reduce startup fees associated with invoking cw-20",
  "code_ids": [ [your-cw20-code-id] ]

And sign and broadcast it:

rebusd tx sign tx_unsigned.json --from validator --chain-id=uni
rebusd tx broadcast tx_signed.json

Likewise, UnpinCodes can unpin already-pinned contracts. The specified code_ids will be unpinned.

Note: For now, you will need to submit these proposals manually as we await upstream CLI support in wasmd.

How does this work? CosmWasm uses an LRU cache to store recently used contracts in memory. Contracts in cache have considerably lower startup times, saving gas. Pinning a contract ensures it doesn't leave validators' caches. Doing so consumes about 20MB per contract on every node, but guarantees startup costs for the contract will be negligible.