Mempool and the Lightening Network

[Dunamisx]

As lightening network is mainly design to provide solution to scalability and a fast and secured transaction while mempool is used in storing any unconfirmed transaction information.

Does the lightening network by any means require the use of mempool in transaction verification or it does byepass mempool?

In other words, could unverified transaction occur with the use of lightening network that may require the service of mempool?

[LoyceV]

In other words, could unverified transaction occur with the use of lightening network that may require the service of mempool?

It depends
Before you can use the Lightning Network, your on-chain transaction needs to be confirmed to open the channel. If mempool is full, high on-chain fees can make it undesirable to open a channel, or your funding transaction will be stuck in mempool for a very long time.
But I've also used Phoenix Wallet's implementation: their channel-opening is custodial, so after funding the wallet, they open a channel for you. But since they open the channel to their own node, they trust it already before it's confirmed. In other words: you can make payments while the transaction that funds your channel is still "stuck" in mempool.

[Rath_]

Does the lightening network by any means require the use of mempool in transaction verification or it does byepass mempool?

Lightning Network nodes need to watch the mempool and the blockchain because they must:

a) check if their channel partner didn't cheat by broadcasting some old channel state (using a revoked commitment transaction),
b) check if any of the known channels' funding transactions have been spent,
c) check if a funding transaction for a specific channel has been confirmed upon receiving "channel_announcement" message.

When you send a transaction over the Lightning Network, you don't need to obtain any data from the mempool. Lightning Network nodes maintain a network graph of all channels so that they can easily and trustlessly calculate a path for the payment. Removal and addition of nodes based on the (un)confirmed transactions is a completely separate process.