Why Deploying to L2 networks in Blockchain / Solidity? - Purpose & Use Cases

The Big Idea

What if your blockchain app could run lightning fast and cost almost nothing to use?

The Scenario

Imagine you have a busy highway (the main blockchain) where every car (transaction) must wait in long lines to get through. You try to add more cars manually, but the traffic jams make everything slow and expensive.

The Problem

Using only the main blockchain means slow transaction times and high fees. Manually managing this congestion is frustrating and costly, like paying a toll every time you want to drive through a crowded city.

The Solution

Deploying to Layer 2 (L2) networks moves many transactions off the busy main highway to faster side roads. This reduces traffic, lowers costs, and speeds up processing without losing security.

Before vs After

✗ Before

deployContract(mainnet, contract)

✓ After

deployContract(L2Network, contract)

What It Enables

It enables fast, cheap, and scalable blockchain applications that users can enjoy without waiting or paying high fees.

Real Life Example

Think of a popular game where thousands of players trade items quickly. Deploying on L2 lets trades happen instantly and cheaply, keeping players happy and the game running smoothly.

Key Takeaways

Manual deployment on mainnet is slow and expensive.

L2 networks reduce congestion and fees by handling transactions off-chain.

Deploying to L2 makes blockchain apps faster and more user-friendly.

Practice

1. What is the main benefit of deploying smart contracts to Layer 2 (L2) networks?

easy

A. Increased decentralization over Layer 1

B. More complex contract code execution

C. Faster transactions and lower fees compared to Layer 1

D. Unlimited storage capacity for contracts

Solution

1. Step 1: Understand Layer 2 purpose

   Layer 2 networks are designed to improve blockchain scalability by handling transactions off the main chain.

2. Step 2: Identify benefits of L2

   This results in faster transaction speeds and lower fees compared to Layer 1.

3. Final Answer:

   Faster transactions and lower fees compared to Layer 1 -> Option C

4. Quick Check:

   L2 improves speed and cost [OK]

Hint: L2 means faster and cheaper transactions than L1 [OK]

Common Mistakes:

• Confusing L2 with increased decentralization
• Thinking L2 allows unlimited storage
• Assuming L2 makes contracts more complex

2. Which of the following is the correct syntax to specify an L2 network in a deployment script using Hardhat?

easy

A. "network: 'layer2'" inside the config file

B. "network: 'l1'" inside the deployment script

C. "network: 'mainnet'" inside the config file

D. network: 'layer2'" without quotes in the script

Solution

1. Step 1: Recognize correct network naming

   In Hardhat config, network names are strings and must be quoted.

2. Step 2: Identify L2 network syntax

   Using "network: 'layer2'" inside the config file is the correct way to specify the L2 network.

3. Final Answer:

   "network: 'layer2'" inside the config file -> Option A

4. Quick Check:

   Network names are strings in config [OK]

Hint: Network names must be strings in config files [OK]

Common Mistakes:

• Using unquoted network names causing syntax errors
• Confusing L1 and L2 network names
• Placing network setting inside deployment script instead of config

3. Given this deployment snippet for an L2 network:

const network = 'layer2';
console.log(`Deploying to ${network}`);

What will be the output?

medium

A. Deploying to ${network}

B. Deploying to layer2

C. Deploying to network

D. Error: network not defined

Solution

1. Step 1: Understand template literals

   The backticks and ${} syntax insert variable values into strings.

2. Step 2: Substitute variable value

   Here, ${network} becomes 'layer2', so the output is 'Deploying to layer2'.

3. Final Answer:

   Deploying to layer2 -> Option B

4. Quick Check:

   Template literal inserts variable [OK]

Hint: Backticks with ${} insert variables in strings [OK]

Common Mistakes:

• Confusing template literals with normal quotes
• Expecting literal ${network} output
• Assuming variable is undefined

4. You try to deploy a contract to an L2 testnet but get an error: "Invalid RPC URL". What is the most likely cause?

medium

A. Your private key is invalid

B. The contract code has syntax errors

C. You forgot to compile the contract

D. The RPC URL for the L2 network is missing or incorrect in the config

Solution

1. Step 1: Understand RPC URL role

   The RPC URL connects your deployment tool to the blockchain network.

2. Step 2: Link error to cause

   An "Invalid RPC URL" error means the URL is missing or wrong in the config file.

3. Final Answer:

   The RPC URL for the L2 network is missing or incorrect in the config -> Option D

4. Quick Check:

   Invalid RPC URL means wrong/missing URL [OK]

Hint: Check RPC URL correctness in config first [OK]

Common Mistakes:

• Assuming contract code errors cause RPC URL errors
• Ignoring network config settings
• Not verifying private key separately

5. You want to deploy a contract to an L2 network but keep your private key secure. Which approach is best?

hard

A. Store the private key in environment variables and load it securely

B. Use a public key instead of a private key for deployment

C. Share the private key in the project README for easy access

D. Hardcode the private key in the deployment script

Solution

1. Step 1: Understand private key security

   Private keys must be kept secret to prevent unauthorized access.

2. Step 2: Identify secure storage method

   Using environment variables keeps keys out of code and version control, enhancing security.

3. Final Answer:

   Store the private key in environment variables and load it securely -> Option A

4. Quick Check:

   Env vars keep keys secret [OK]

Hint: Never hardcode keys; use environment variables [OK]

Common Mistakes:

• Hardcoding keys in scripts
• Sharing keys publicly
• Confusing public and private keys