Blockscout is an open-source blockchain explorer for EVM-compatible chains, written in Elixir using the Phoenix framework. It indexes and serves on-chain data including blocks, transactions, internal transactions, token transfers, token balances, contract code, and more. The system is composed of four umbrella apps: `explorer` (database schemas, chain import pipeline, caching), `block_scout_web` (Phoenix web server with REST API v2, JSON-RPC, GraphQL, and real-time WebSocket channels), `indexer` (background fetchers that pull data from Ethereum nodes using JSON-RPC), and `ethereum_jsonrpc` (transport abstraction with chain-specific variants for Geth, Nethermind, Besu, etc.). The architecture is a monolith with clear separation of concerns, using PostgreSQL as the primary store, ETS/ConCache for caching, and Oban for async job processing. It supports multiple chain types (Ethereum, Optimism, Arbitrum, Celo, ZkSync, Scroll, and more) via compile-time and runtime configuration, with chain-specific data models and import pipelines. External dependencies include a PostgreSQL database, an Ethereum JSON-RPC endpoint, optional microservices for smart contract verification (Rust verifier, Sourcify), and third-party market data providers (CoinGecko, DefiLlama). The frontend is a single-page application built with jQuery and custom JavaScript, with real-time updates via Phoenix Channels. The codebase is well-structured with extensive use of Elixir behaviours (BufferedTask, Import.Runner, FillingMigration) and a sophisticated caching layer. It is actively maintained with frequent releases, thorough CI/CD, and a large community.