SELECT 
  * 
FROM 
  cscart_vd_vendor_optional_questions 
WHERE 
  brand_id = 339

Query time 0.00031

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_vd_vendor_optional_questions",
          "access_type": "ref",
          "possible_keys": ["brand_id"],
          "key": "brand_id",
          "key_length": "4",
          "used_key_parts": ["brand_id"],
          "ref": ["const"],
          "rows": 2,
          "filtered": 100
        }
      }
    ]
  }
}

Result

id brand_id optional_data
339 339 {"model_of_clothing":null,"pieces_per_model":null,"people_on_brand":null,"products_made_mexico":null,"production_method":null,"brand_birth_year":null,"use_images":null,"name_optional":null,"ethnicity_optional":null,"newsletter":null,"newsletter_email":null,"council_participation":null,"slow_fashion_marketplace":null,"anything_else_txt":null,"fashion_revolution_awareness":null,"fashion_revolution_events":null,"fashion_revolution_importance":null,"fashion_revolution_interview":null}