> For the complete documentation index, see [llms.txt](https://polarischain-1.gitbook.io/polarischain/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://polarischain-1.gitbook.io/polarischain/5.-system-architecture-and-network-economics/5.1-layered-architecture-design.md).

# 5.1 - Layered Architecture Design

Polarischain follows a five-layer modular stack, separating concerns to enable independent optimization, auditability, and upgrade pathways:

1. **Application Layer:** Hosts the full node binary, wallet CLI, block explorer, application-level P2P service, and the blockchain state manager that processes ordered transactions into account balances and asset registries.
2. **Consensus Layer:** Implements DAG-based BFT consensus, including the block store, write-ahead log (WAL), universal committer, linearizer, epoch manager, and validator-to-validator networking.
3. **Cryptography Layer:** Provides NIST-standardized post-quantum primitives: CRYSTALS-Dilithium2 (ML-DSA-44) signatures, ML-KEM-768 key encapsulation, BLAKE2b-256 hashing, AES-256-GCM authenticated encryption, and Argon2id-based key derivation.
4. **Storage Layer:** Combines LMDB for hot state (balances, nonces, faucet claims) via zero-copy memory-mapped reads, and RocksDB for cold/historical data (blocks, asset metadata, indices) with strict column-family isolation. A memory-mapped WAL ensures crash recovery, while per-store encryption-at-rest protects persisted data.
5. **Network Layer:** Uses persistent TCP P2P with LZ4 message compression, length-prefixed framing, protocol versioning, peer health tracking, and PQXDH post-quantum transport encryption. Connection management enforces per-IP and per-authority controls to mitigate spam and DDoS vectors.


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