alchemy-sdk-patterns

# Alchemy SDK Patterns ## Overview Production patterns for the `alchemy-sdk` package: singleton clients, multi-chain factories, response caching, and type-safe contract wrappers. ## Instructions ### Step 1: Multi-Chain Client Factory ```typescript // src/alchemy/client-factory.ts import { Alchemy, Network } from 'alchemy-sdk'; type ChainName = 'ethereum' | 'polygon' | 'arbitrum' | 'optimism' | 'base'; const NETWORK_MAP: Record<ChainName, Network> = { ethereum: Network.ETH_MAINNET, polygon: Network.MATIC_MAINNET, arbitrum: Network.ARB_MAINNET, optimism: Network.OPT_MAINNET, base: Network.BASE_MAINNET, }; class AlchemyClientFactory { private static clients = new Map<string, Alchemy>(); static getClient(chain: ChainName): Alchemy { if (!this.clients.has(chain)) { this.clients.set(chain, new Alchemy({ apiKey: process.env.ALCHEMY_API_KEY, network: NETWORK_MAP[chain], maxRetries: 3, })); } return this.clients.get(chain)!; } static getAllClients(): Map<ChainName, Alchemy> { for (const chain of Object.keys(NETWORK_MAP) as ChainName[]) { this.getClient(chain); } return this.clients as Map<ChainName, Alchemy>; } } export { AlchemyClientFactory, ChainName }; ``` ### Step 2: Response Caching Layer ```typescript // src/alchemy/cache.ts interface CacheEntry<T> { data: T; expiresAt: number; } class AlchemyCache { private cache = new Map<string, CacheEntry<any>>(); private defaultTtlMs: nu...