SELECT 
  search_phrases 
FROM 
  cscart_ab__search_motivation 
WHERE 
  category_id = 318 
  AND lang_code = 'en'

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_ab__search_motivation",
          "access_type": "ref",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["category_id"],
          "ref": ["const"],
          "rows": 1,
          "filtered": 100,
          "index_condition": "cscart_ab__search_motivation.lang_code = 'en'"
        }
      }
    ]
  }
}