SELECT 
  company_id 
FROM 
  tconnect_wk_vendor_subdomain 
WHERE 
  subdomain = 'tconnect' 
  AND status = 'A'

Query time 0.00060

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}