Crypto Exchange — Detailed

flowchart TB
  subgraph Apps
    WEB
    APP([Mobile])
    API[Pro / FIX API]
  end

  subgraph Edge
    CDN
    GW
    WAF
    RL[Rate limit]
  end

  subgraph Trade[Trading]
    ME[Matching Engine<br/>per market]
    OB[(Order book)]
    EVT[[Event log]]
    RISK[Pre-trade risk]
  end

  subgraph Custody[Custody]
    HOT[Hot wallet]
    WARM[Warm wallet multi-sig]
    COLD[Cold wallet / HSM]
    SWEEP([Sweeper jobs])
  end

  subgraph Chain[Chains]
    BTC[Bitcoin node]
    ETH[Ethereum node]
    EVM[Other EVM]
    SOL[Solana]
    CONF[Confirmation watchers]
    MEMP[Mempool monitor]
  end

  subgraph Ledger
    LED[(Internal ledger<br/>double-entry)]
    BAL[Balance projection]
    DEP[Deposits]
    WD[Withdrawals]
  end

  subgraph Risk[Risk & Compliance]
    KYC[KYC / KYB]
    AML[AML monitoring]
    SAN[Sanctions screening]
    TRAV[Travel rule]
    LIM[Withdrawal limits]
  end

  subgraph Mkt[Market Data]
    L1[L1/L2 feeds]
    WSF([WS feeds to clients])
    HIST[(Historical OHLCV)]
  end

  subgraph Ops
    OBSV[Metrics / traces]
    RUNB[Runbooks]
    SOC[24x7 SOC]
  end

  Apps --> CDN --> GW --> RL --> Trade
  Trade --> Ledger
  Ledger --> Custody
  Custody --> Chain
  Risk --- Apps
  Risk --- Custody
  Mkt --- Trade

    classDef client fill:#dbeafe,stroke:#1e40af,stroke-width:1px,color:#0f172a;
    classDef edge fill:#cffafe,stroke:#0e7490,stroke-width:1px,color:#0f172a;
    classDef service fill:#fef3c7,stroke:#92400e,stroke-width:1px,color:#0f172a;
    classDef datastore fill:#fee2e2,stroke:#991b1b,stroke-width:1px,color:#0f172a;
    classDef cache fill:#fed7aa,stroke:#9a3412,stroke-width:1px,color:#0f172a;
    classDef queue fill:#ede9fe,stroke:#5b21b6,stroke-width:1px,color:#0f172a;
    classDef compute fill:#d1fae5,stroke:#065f46,stroke-width:1px,color:#0f172a;
    classDef storage fill:#e5e7eb,stroke:#374151,stroke-width:1px,color:#0f172a;
    classDef external fill:#fce7f3,stroke:#9d174d,stroke-width:1px,color:#0f172a;
    classDef obs fill:#f3e8ff,stroke:#6b21a8,stroke-width:1px,color:#0f172a;
    class APP,WSF client;
    class API,RL,ME,RISK,HOT,WARM,COLD,BTC,ETH,EVM,SOL,CONF,MEMP,BAL,DEP,WD,KYC,SAN,TRAV,LIM,L1,RUNB,SOC service;
    class OB,LED,HIST datastore;
    class EVT queue;
    class SWEEP compute;
    class AML,OBSV obs;

Deposits & withdrawals

• Each user gets unique deposit addresses per chain.
• Watcher confirms N blocks → credit internal ledger.
• Withdrawal: sign tx from hot wallet; if exceeds threshold, route to warm/cold multi-sig.

Custody best practices

• 95%+ assets cold; rotate keys; geographically separate signers.
• Hot wallet sized to expected withdrawal flow only.

Matching

• Same as stock exchange but with crypto pairs.
• Often higher tx volume, lower per-order latency requirements.

Glossary & fundamentals

Concepts referenced in this design. Each row links to its canonical page; the tag column shows whether it is a high-level (HLD) or low-level (LLD) concept.

Tag	Concept	What it is	Page
HLD	CDN	edge caching for static assets	cdn
HLD	LSM vs B-Tree engines	WAL, memtable, SSTables, compaction	storage-engines-lsm-btree
HLD	Observability	metrics, logs, traces, SLOs	observability