SELECT 
  * 
FROM 
  cscart_users 
WHERE 
  `company_id` = '3389'

Query time 0.46713

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "table_name": "cscart_users",
      "access_type": "ALL",
      "rows": 299997,
      "filtered": 100,
      "attached_condition": "cscart_users.company_id = '3389'"
    }
  }
}

Result

user_id status user_type user_login referer is_root company_id subdomain last_login last_activity timestamp password salt firstname lastname company email phone fax url tax_exempt lang_code birthday purchase_timestamp_from purchase_timestamp_to responsible_email password_change_timestamp api_key janrain_identifier partner_id card_number valid_thru card_holder_name two_steps_auth_secret remember_data is_shopify email_code verify_email c_state c_country zipcode email_verification_otp helpdesk_user_id first_login_flag downgrade_plan_status is_card plan_id plan_status payment_token downgrade_plan_id invest_terms_flag is_subuser passport_customer_id is_vendor_subuser main_vendor_user_id
306523 A V user_306523 Y 3389 1708508592 1726128817 1675210805 $2y$10$NCJavO14TCEcxfvjG7HTzejgqIfkucCx63NbH0BzWw7MrrVYpVVdS Coach Demo Coach staging2merchanttwo@yopmail.com (661) 286-4334 N en 0 0 0 1708497862 0 0 CA US 01342 0 1 0 0 N N 0