How to Query Pending Mempool Transactions Using Ethers.js

JavaScript provides three main approaches for handling asynchronous code: callbacks (the first solution, which can lead to 'callback hell' when nesting multiple asynchronous operations), Promises (the second solution, which use .then() and .catch() for better readability and error handling), and async/await (the modern solution that makes asynchronous code appear synchronous and more readable). Promises solve the callback hell problem by allowing sequential asynchronous operations to be written in a linear fashion, while async/await further simplifies the syntax by enabling developers to write asynchronous code that looks like synchronous code, making it easier to understand and maintain.

Asynchronous JavaScript enables non-blocking execution of tasks through three main patterns: callbacks (functions passed as arguments to establish dependencies between operations), promises (objects representing eventual completion with pending, resolved, or rejected states that enable cleaner chaining and error handling), and async/await (syntactic sugar over promises that makes asynchronous code appear synchronous while maintaining non-blocking behavior); these patterns allow JavaScript to perform multiple operations concurrently rather than sequentially, improving application responsiveness and efficiency.

Promises have three states: pending, fulfilled, and rejected. Promise.all() waits for all promises to resolve, rejecting if any reject. Promise chaining links asynchronous operations, with .catch() handling rejections. Promise.resolve() and Promise.reject() create resolved/rejected promises. Understanding promises is essential for modern asynchronous JavaScript programming.

Promises are standardized JavaScript objects that represent future values, existing in three states: pending (waiting for work to complete), fulfilled (successful completion with a value), or rejected (error occurred). They solve the 'pyramid of doom' problem by allowing you to chain asynchronous operations using .then(), which returns a new promise, enabling flat, readable code instead of nested callbacks. Async/await is syntactic sugar built on top of promises, using the async keyword to mark a function and await to pause execution until a promise resolves, making asynchronous code look and behave like synchronous code while maintaining the underlying promise-based workflow.

JavaScript handles asynchronous operations through three main approaches: callbacks (functions passed as arguments that execute after an operation completes), promises (objects representing the eventual completion of an asynchronous operation with states like pending, resolved, or rejected), and async/await (syntactic sugar that makes asynchronous code appear synchronous). This evolution from callbacks to promises to async/await improves code maintainability by allowing code to grow vertically instead of horizontally, making asynchronous operations easier to read, debug, and manage while still leveraging JavaScript's non-blocking execution model.

This section explains the core concepts of Ethers library architecture. A Provider is used for reading from the blockchain, like looking at a car's exterior and interior without being able to move it. A Signer is used for changing the state of the chain, like having the key to move the car. Signer requires a private key or seed and needs to fund transactions. The section demonstrates using curl commands to interact with Moonbeam's JSON-RPC interface, showing how to use eth_getBalance with address and block tag parameters. It also explains the difference between local Dev nodes (state resets each time) and shared networks like Moonbase Alpha (state persists across sessions).

Ethers.js implements a three-layer architecture for Ethereum interactions: Providers (read-only access to blockchain data), Signers (write access enabling transaction signing), and Contracts (abstractions built on top of signers). The workflow involves creating a provider connected to the network, obtaining a signer from the provider, and then constructing a contract instance using the contract address, ABI, and signer. This layered approach separates concerns and enables secure, efficient blockchain interactions.

This comprehensive section covers the foundational elements of Ethereum development using Ethers.js. It begins with installing and configuring Ethers.js in a Node.js project, explaining package management concepts like package.json and package-lock.json. The video establishes the mental model of providers as intermediaries between applications and the Ethereum blockchain, comparing them to API keys in web2 services. Three provider types are explored: default providers for testing, Infura/Alchemy services (centralized with rate limits), and local nodes (fully decentralized). The section demonstrates practical provider usage including fetching block numbers, resolving ENS names, and retrieving account balances. Critical to Ethereum development is understanding asynchronous programming patterns using Promises and async/await, as all blockchain interactions return Promises.

Ethers.js is a JavaScript library that simplifies Ethereum blockchain interaction by abstracting complex RPC calls; it enables developers to query blockchain data through Providers, sign transactions using Wallet/Signer objects, send Ether between accounts, and interact with smart contracts by deploying ABI interfaces to read data or write state changes, with all Ethereum values represented in wei (10^18 smallest unit) rather than decimal ether.

The instructor demonstrates using ethers.js to interact with the blockchain. A browser provider connects to MetaMask (window.ethereum) to access the user's wallet. A signer object is obtained after the user approves the app to use their wallet, allowing the app to read the user's address. The instructor emphasizes the importance of using ethers.js version 6, as version 5 documentation may be outdated. The signer is essential for creating and signing transactions, and the instructor shows how to save it in React state for later use.

The network hash rate is 180 trillion hashes per second, while miners generate 4 billion nonces per second. These nonces are exhausted in approximately 4 × 10^-9 seconds, far faster than a one-second time window. This creates a critical timing challenge: miners cannot wait for a full second to find a valid hash because their nonce supply would be depleted long before. The mempool (memory pool) is introduced as the solution, serving as an area where all unconfirmed transactions are stored before being included in blocks. The mempool is distributed across nodes and miners, similar to how the blockchain is distributed.

The mempool (memory pool) is a data structure that stores all valid but unconfirmed transactions in the network. When a miner finds a block, they include transactions from the mempool in that block. The mempool ensures that transactions are not lost even if they are not immediately included in a block. Transactions in the mempool are propagated to all miners, who can then include them in their own blocks. This design provides resilience and ensures that the network can recover from temporary forks or network partitions.

The mempool (memory pool) is the storage space for unconfirmed Bitcoin transactions. When a user sends a transaction, the recipient sees it immediately because the network distributes transaction information dezentralized. However, the transaction is not yet confirmed, which is why it may take 2-6 blocks (2-6 confirmations) before the transaction is fully finalized on the blockchain.

The mempool is a decentralized storage area where all unconfirmed transactions are temporarily held before being included in blocks; every node and miner in the network maintains their own copy of the mempool, and transactions propagate through the network until miners select them for inclusion in blocks, which are then validated and added to the blockchain.

The mempool (memory pool) is the waiting area for unconfirmed transactions in the Bitcoin network. Currently, over 430,000 transactions are waiting for confirmation, with 200 blocks queued up. This represents an unprecedented level of congestion. The video notes that while high transaction volumes occurred in 2021, the current situation with unconfirmed transactions is unique. The blocks are becoming increasingly full, and miners cannot process transactions fast enough to clear the backlog.

HTTP uses a distinct connection for each request, increasing server load as new handshakes must be created for every request and connections are closed after completion. In contrast, WebSocket connections are persistent and remain open as long as neither party interrupts them. The WebSocket protocol is an independent TCP-based protocol, with its only relationship to HTTP being that its handshake is interpreted by HTTP servers as an upgrade request.

HTTP is a request-response protocol where servers can never push events directly to clients. This limitation becomes problematic for realtime applications like chat systems or collaborative tools where immediate updates are essential. Long polling and Server-Side Events are alternatives but have drawbacks like unnecessary server load and delays. WebSockets solve these problems by establishing persistent connections that remain open until explicitly closed, enabling both clients and servers to send data at any time without waiting for the other party to initiate communication.

HTTP is request-response while WebSocket is full-duplex persistent connection. WebSockets begin with HTTP upgrade requests (Upgrade header, Sec-WebSocket-Key) and respond with 101 Switching Protocols. Messages are transmitted as frames with headers containing flags and payload length. Go's standard library lacks full WebSocket support; gorilla/websocket is recommended. Libraries should be vendored for production stability.

WebSockets provide full-duplex communication over a single TCP connection, standardized as RFC 6455 by IETF. Key advantages include real-time data transfer without lag, bidirectional communication enabling server-to-client pushes, efficiency through reduced overhead (no headers per message), and persistent connections minimizing latency. Common use cases include chat applications, real-time gaming, collaborative editing, live updates, and IoT. Three fundamental differences from HTTP: unidirectional vs. bidirectional communication, closing connections after each request vs. persistent open connections, and lack of server push capability in traditional HTTP.

This comprehensive comparison covers the fundamental differences between HTTP and WebSocket protocols. HTTP operates on a request-response model where connections close after each exchange, requiring repeated connection establishment for real-time applications. This creates latency issues due to keep-alive timers and connection overhead. WebSocket, in contrast, enables persistent full-duplex connections through an upgrade mechanism, allowing simultaneous bidirectional communication without waiting for responses. The key advantages include server push capability, continuous connection maintenance, and reduced overhead for real-time applications.