SELECT 
  MIN(point_price) 
FROM 
  cscart_product_point_prices 
WHERE 
  product_id = 31 
  AND lower_limit = 1 
  AND usergroup_id IN (0, 0, 1)

Query time 0.00019

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost": 0.004452,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_point_prices",
          "access_type": "ref",
          "possible_keys": ["unique_key", "src_k"],
          "key": "src_k",
          "key_length": "5",
          "used_key_parts": ["product_id", "lower_limit"],
          "ref": ["const", "const"],
          "loops": 1,
          "rows": 2,
          "cost": 0.004452,
          "filtered": 100,
          "index_condition": "cscart_product_point_prices.usergroup_id in (0,0,1)"
        }
      }
    ]
  }
}