SELECT 
  variant_id, 
  yml2_unit 
FROM 
  cscart_product_feature_variant_descriptions 
WHERE 
  variant_id IN (
    '5180', '5179', '4790', '4778', '4766', 
    '4807', '4763', '4783', '4773', '4776', 
    '4780', '5163', '5164', '4862', '3095', 
    '3097', '3096', '3099', '3098', '4922', 
    '4981', '5139', '3100', '3101', '5074', 
    '3103', '4974', '5063', '4983', '3085', 
    '4915', '3686', '3087', '3088', '3089', 
    '3092', '3093', '3094', '3104', '3084', 
    '4904', '1870', 'Y'
  ) 
  AND lang_code = 'uk'

Query time 0.00064

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_feature_variant_descriptions",
          "access_type": "range",
          "possible_keys": ["PRIMARY"],
          "key": "PRIMARY",
          "key_length": "9",
          "used_key_parts": ["variant_id", "lang_code"],
          "rows": 43,
          "filtered": 100,
          "index_condition": "cscart_product_feature_variant_descriptions.variant_id in ('5180','5179','4790','4778','4766','4807','4763','4783','4773','4776','4780','5163','5164','4862','3095','3097','3096','3099','3098','4922','4981','5139','3100','3101','5074','3103','4974','5063','4983','3085','4915','3686','3087','3088','3089','3092','3093','3094','3104','3084','4904','1870','Y') and cscart_product_feature_variant_descriptions.lang_code = 'uk'"
        }
      }
    ]
  }
}