GP 14: Migrate BOB pool to USDC on Polygon

The proposal was confirmed and executed.

• Polygon Safe Transactions #32 and #33

• Polygon txs:

  • 32: https://polygonscan.com/tx/0xfc792b0693fb6d5951085310d1aa0e1edb6932ceedbeb7a15434f89416778002

  • 33: https://polygonscan.com/tx/0x7cf8f47d95b7e38eea8c9b2b1110d3ce4602f2936f70cdc44a5fa670923e7d58

Proposal objective

This proposal is to replaces the underlying token from BOB to USDC for the zkBob pool on Polygon as discussed with the community.

The migration will replace the zkBob pool implementation to the new contract 0x5e93FA8819Bc074C717a92240a1689D1B81aAFcd and the Direct Deposit Queue implementation to 0x22299414E9e0E7663f8977a7EA6c1908F2167181. To allow further swaps of USDC to MATIC as part of the withdrawal process the Token Seller contract will be replaced by 0xDb53D01947252A5bEb488991971D8436AA2828A5.

All BOB owned by the zkBob pool contract will be swapped to USDC using BobSwap. The amount of BOB tokens paid as fees on BobSwap will be reimbursed with the corresponding amount of USDC from the Governance Safe account. The logic of the tokens swap is defined in the migrationToUSDC() method of the pool.

Proposal breakdown

To avoid undesirable interactions with the zkBob pool before the migration the proposal consists of two steps:

Step 1: Disable direct deposits

Transaction #32 in the Safe on Polygon contains two three setLimits calls to disallow users from transfering tokens directly to the pool by setting limits for tier 0, 1 and 254 to zero for direct deposits. Interim limits are set to the following values:

Tier	Single deposit	Daily user deposit	Daily deposit	Daily withdrawal	Pool size	Single DD
Default, id 0	10,000 BOB	10,000 BOB	300,000 BOB	300,000 BOB	2,000,000 BOB	0 BOB
KYC, id 254	20,000 BOB	20,000 BOB	300,000 BOB	300,000 BOB	2,000,000 BOB	0 BOB
Partners, id 1	100,000 BOB	100,000 BOB	300,000 BOB	300,000 BOB	2,000,000 BOB	0 BOB

Step 1 is executed 15 minutes prior to step 2.

Step 2: Migrate the pool from BOB to USDC

Transaction #33 in the Safe executes the following calls:

• increase allowance of the pool contract 0x72e6B59D4a90ab232e55D4BB7ed2dD17494D62fB to transfer USDC from the Governance Safe via theapprove call to the USDC token contract 0x2791Bca1f2de4661ED88A30C99A7a9449Aa84174.
• upgrade the pool implementation with upgradeToAndCall . The method migrationToUSDC() (selector c4a688b8) is invoked after the upgrade.

• remove allowance of the pool contract to transfer USDC from Governance Safe via the approve call made to the USDC token contract 0x2791Bca1f2de4661ED88A30C99A7a9449Aa84174.
• upgrade the implementation of the direct deposit queue 0x668c5286eAD26fAC5fa944887F9D2F20f7DDF289 using the upgradeTo call.
• configure new Token Seller contract on the pool using setTokenSeller.

• the remaining three calls invoke setLimits corresponding to tiers 0, 1 and 254. The recovered limits are:

Tier	Single deposit	Daily user deposit	Daily deposit	Daily withdrawal	Pool size	Single DD	Daily user DD
Default, id 0	10,000 USDC	10,000 USDC	300,000 USDC	300,000 USDC	2,000,000 USDC	1,000 USDC	10,000 USDC
KYC, id 254	20,000 USDC	20,000 USDC	300,000 USDC	300,000 USDC	2,000,000 USDC	1,000 USDC	10,000 USDC
Partners, id 1	100,000 USDC	100,000 USDC	300,000 USDC	300,000 USDC	2,000,000 USDC	1,000 USDC	10,000 USDC

Additional verification

The migration procedure was verified using the following Foundry-script.

Another script verifies the correctness of the Safe transactions execution. The script could be placed to script/scripts directory of the zkBob contracts repo. The command to run the script is forge script -vvv -rpc-url <https://rpc.ankr.com/polygon> script/scripts/BOBPoolMigrationVerification.s.sol