[
  {
    "merchant_id": "MC-10229",
    "valid_from": "2026-05-11T00:00:00+09:00",
    "sales_tier": "영세",
    "fee_rate_bp": 220,
    "settlement_days": 5
  },
  {
    "merchant_id": "MC-10229",
    "valid_from": "2026-08-14T00:00:00+09:00",
    "sales_tier": "영세",
    "fee_rate_bp": 220,
    "settlement_days": 5
  },
  {
    "merchant_id": "MC-10229",
    "valid_from": "2026-10-08T00:00:00+09:00",
    "sales_tier": "영세",
    "fee_rate_bp": 220,
    "settlement_days": 2
  }
]