SELECT 
  service_id 
FROM 
  cscart_shipping_services 
WHERE 
  module = 'ghn' 
  AND code = 'delivery_basic'

Query time 0.00015

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_shipping_services",
          "access_type": "ALL",
          "rows": 259,
          "filtered": 100,
          "attached_condition": "cscart_shipping_services.module = 'ghn' and cscart_shipping_services.`code` = 'delivery_basic'"
        }
      }
    ]
  }
}