Large deposits over certain Layer 2 (L2) networks can be subjected to delays given the need for bridging.
In most instances, deposits will be processed on Optimism in just a matter of minutes. In rare cases, very large deposits or deposits made during periods of very high bridging activity may take up to seven days to be credited to your Coinbase account.
L2 blockchains, such as Optimism, institute a delay as a way to protect the security of their network. On Optimism, this is called a challenge period. If a very large deposit to Coinbase incurs a deposit processing delay, smaller deposits may continue to be processed at a normal speed.
Large deposits over L2 networks which can be subjected to a delay includes:
Arbitrum
Base
Optimism
Polygon