This is the original zkSync L2 scaling monorepo (zkSync Lite), implementing a ZK-rollup on Ethereum with low-gas ETH/ERC20 transfers, plus NFTs, swaps, and forced exits. The code is primarily a Rust backend with multiple binaries and services: the core state-keeper/committer (`zksync_core`), REST/JSON-RPC/Web3 API server (`zksync_api`), PLONK prover and witness generator, Ethereum transaction sender, event listener, data-restore tool, and exit-tree generator. It also contains Solidity smart contracts, JavaScript/Rust SDKs, a TypeScript integration test suite, and a large PostgreSQL storage layer with Diesel migrations. In production, the system receives L1 deposits and L2 transactions, validates them in a mempool, builds pending blocks in the state keeper, generates witnesses and proofs, and commits/verifies/executes blocks on Ethereum. The API exposes account, transaction, fee, and NFT endpoints, with WebSocket event notifications. The main external dependencies are Ethereum (via web3/ethabi), PostgreSQL, CoinGecko/CoinMarketCap price feeds, and custom `franklin_crypto`/`rescue`/`jubjub` zero-knowledge circuit libraries. The project is now in a deprecation/sunset phase: zkSync Lite is no longer the active product, and the `exit_tree_generator`/exit-tool paths exist primarily to help users withdraw funds. Architecturally, the monorepo is modular and contains several well-isolated patterns worth studying: a generic `Balancer` for channel-based load distribution, an async shared LRU cache, and generic serde wrappers for hex/BigUint/ratio serialization. These components demonstrate solid Rust engineering, but the repository also carries substantial legacy weight: multiple contract and schema versions, ignored tests, hardcoded development keys, old dependency versions, deprecated testnets, and a custom crypto fork. It is best treated as a reference for the original zkSync architecture or as a base for maintaining a sunset service, not as a codebase to absorb as a whole.