How Paychainly Sweeps Funds: Gas Top-Up, USDT Transfer, and Fee Deduction Explained

Why Sweeping Is Needed

Each customer gets a unique deposit address derived from your HD wallet. Funds land there, but you need them in a single master wallet for treasury management. Paychainly automates this with a three-step sweep pipeline.

Step 1 — BNB Gas Top-Up

USDT transfers require BNB for gas. The gas wallet sends a small amount of BNB (default 0.002 BNB ≈ $1) to the deposit address before sweeping. A per-address Redis lock prevents concurrent gas top-ups to the same address.

Step 2 — USDT Transfer

Once BNB arrives, the platform calls transfer(masterAddress, balance) on the USDT ERC-20 contract from the deposit address private key (derived from your MASTER_SEED mnemonic).

Step 3 — Fee Deduction

The platform fee is deducted before crediting you:

fee = Math.max(feeFlat, balance × feePercent / 100)
// default: max($0.60, 1% of payment)

netAmount = balance − fee − gasReimbursement

Gas reimbursement is the actual BNB cost converted to USDT via the PancakeSwap V2 price feed — you never pay more than the real gas cost.

Step 4 — Leftover BNB Returned

Any unused BNB in the deposit address is transferred back to the gas wallet, keeping it funded for future sweeps without manual top-ups.

Concurrency Control

• Per-address Redis lock prevents double-sweep of the same address.
• Gas wallet nonce collision is prevented by GasWalletLockService.
• Up to 5 addresses are swept in parallel (configurable via SWEEP_CONCURRENCY).