RPC Polling vs WebSockets: Market Latency

Simple Implementation: Uses standard HTTP/HTTPS requests. This matters for prototyping, simple dashboards, or serverless functions where you don't want to manage persistent connections. Libraries like ethers.js and web3.py handle retries and batching out-of-the-box.

Latency = Poll Interval: Data freshness is bound by your request frequency (e.g., 2-second polls). This results in 100ms - 5s+ latency for new blocks/events. This matters for non-critical data like historical analytics, batch processing, or user balances where sub-second updates aren't required.

Event-Driven Updates: Receive new block headers and event logs as they are mined, typically in < 100ms. This matters for high-frequency dApps like DEX arbitrage bots, NFT mint monitors, or live trading interfaces where being first to see the transaction is critical.

Connection Management: Requires handling reconnections, backoff, and state synchronization. Providers like Alchemy, QuickNode, and Chainscore offer managed WebSocket endpoints, but you still need robust client-side logic. This matters for production systems where you must guarantee uptime and message integrity.

Pay-Per-Request Model: With providers like Infura and Public RPCs, you pay only for the requests you make. For applications with predictable, low-frequency queries (e.g., 1 request/user session), this can be >50% cheaper than maintaining always-on WebSocket connections for thousands of users.

Subscribe to Logs & Pending Txs: Native support for eth_subscribe to streams like newHeads or logs. This matters for DeFi protocols monitoring liquidity events, wallet apps showing instant confirmations, or oracles like Chainlink needing immediate on-chain data triggers.

Fixed, per-request billing: Pay only for the data you explicitly fetch. This matters for applications with predictable, low-frequency data needs (e.g., daily portfolio dashboards). Avoids the cost of maintaining a persistent connection for idle periods.

No connection state management: Uses standard HTTP/HTTPS, simplifying load balancing and scaling. This matters for serverless functions (AWS Lambda, Vercel) and batch processing jobs where managing persistent WebSocket connections adds complexity.

Persistent, bidirectional connection: Eliminates HTTP overhead for each update, enabling <100ms market data delivery. This matters for high-frequency trading bots, live NFT mint trackers, and real-time wallet activity feeds where speed is critical.

Server-pushed updates: Receive new blocks, pending transactions, and log events instantly without wasteful polling loops. This matters for monitoring smart contract events (e.g., Uniswap swaps, Aave liquidations) and reduces RPC call volume by up to 90% for active listeners.

Polling interval bottleneck: Even aggressive 1-second polling can miss critical events between calls, creating arbitrage opportunities for faster bots. This matters for MEV-sensitive applications and creates stale price feeds for DEX aggregators like 1inch.

Stateful connection management: Requires handling reconnection logic, heartbeats, and backpressure. At scale (10k+ connections), this increases infrastructure complexity and cost compared to stateless HTTP. This matters for applications with sporadic, bursty traffic patterns.

Specific advantage: No persistent connection overhead. This matters for batch processing and cron jobs where near-real-time updates are not critical. Use cases like daily portfolio snapshots or historical data analysis can operate effectively with 30-60 second intervals, minimizing RPC call costs on providers like Alchemy or Infura.

Specific advantage: Stateless HTTP requests. This matters for serverless functions (AWS Lambda, Vercel) and static frontends where managing WebSocket lifecycle (reconnects, heartbeats) adds complexity. Frameworks like Ethers.js and Viem handle polling loops with simple setInterval patterns.

Specific disadvantage: Inherent delay between polls. This is critical for liquidations, arbitrage bots, and NFT mint monitors where sub-second reaction times are required. A 2-second poll interval on a fast chain like Solana or Avalanche can mean missing dozens of blocks and profitable opportunities.

Specific disadvantage: Redundant data transfer and failed calls. This matters at scale, where high-frequency applications waste bandwidth on empty responses. Polling for rare events (e.g., specific NFT sales) results in thousands of "no-op" calls, increasing costs and potentially hitting provider rate limits.

Specific advantage: Push-based notifications for new blocks and logs. This matters for DEX aggregators (1inch, UniswapX) and perpetual futures platforms that require <100ms latency on price feeds and order book updates. Providers like QuickNode and BlastAPI offer dedicated WebSocket endpoints for this.

Specific advantage: Single persistent connection per stream. This matters for high-throughput dApps monitoring multiple addresses or smart contracts (e.g., DeFi dashboards). It eliminates redundant data transfer, reducing bandwidth and compute costs for applications using The Graph for indexed queries or Pyth for oracles.

Specific disadvantage: Requires handling reconnects and state. This is critical for mobile applications with spotty networks and scalable backends that must manage thousands of concurrent connections. Libraries like Socket.IO add abstraction but introduce latency; native ws libraries are performant but complex.

Specific disadvantage: Premium pricing tiers and scaling challenges. This matters for bootstrapped projects or those with unpredictable user counts. Providers often charge 2-3x more for WebSocket connections versus standard HTTP RPC. Scaling a self-hosted node with WebSocket support (e.g., Geth, Erigon) requires significant DevOps expertise.