SELECT 
  cscart_products.* 
FROM 
  cscart_products 
WHERE 
  cscart_products.product_id IN (
    966, 967, 968, 969, 970, 971, 972, 973, 
    974, 975, 976, 977
  )

Query time 0.00081

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_products",
      "access_type": "range",
      "possible_keys": ["PRIMARY"],
      "key": "PRIMARY",
      "key_length": "3",
      "used_key_parts": ["product_id"],
      "rows": 12,
      "filtered": 100,
      "index_condition": "cscart_products.product_id in (966,967,968,969,970,971,972,973,974,975,976,977)"
    }
  }
}