TL;DR
gRPC is a high-performance data streaming protocol used on Solana to receive real-time blockchain updates (new transactions, account changes, slot updates) with lower latency than standard RPC polling.
Standard RPC works via request-response: you ask for data, the server replies. To get real-time updates, you have to poll repeatedly (e.g., check for new transactions every 200ms). gRPC uses streaming: you subscribe once and the server pushes updates to you instantly as they happen. This reduces latency and bandwidth, making it ideal for applications that need to react to on-chain events in real time.
Trading bots use gRPC to detect new token launches, monitor price changes, and track wallet activity in real time. MEV searchers use gRPC to see pending transactions and submit bundles. Price feeds stream bonding curve updates via gRPC. Any application that needs to react to on-chain events faster than polling allows benefits from gRPC. Yellowstone (by Triton) is the standard gRPC interface for Solana validators.
gRPC endpoints are offered by specialized providers like Helius, Triton, and Kaldera. They’re typically more expensive than standard RPC because they require validators running modified software (Geyser plugins) that can stream account and transaction updates. For most retail traders, gRPC access through their trading bot’s infrastructure is sufficient. Direct gRPC access matters more for developers building custom tools.