Crypto exchange reconciliation

Design a continuous internal-consistency reconciliation system for a crypto exchange that must prove, on an ongoing basis, that internal user balances (the exchange's ledger) match actual on-chain + custodial holdings, across ~20 assets and millions of accounts. Deposits/withdrawals settle on-chain with confirmation delays and reorgs. The system must detect any drift (a user credited but funds not actually received, or holdings unaccounted for) quickly. Describe the architecture and how you handle blockchain-specific consistency hazards.