SELECT 
  state_id 
FROM 
  cscart_states 
WHERE 
  code = 'Singapore' 
  AND country_code = 'SG'

Query time 0.00025

JSON explain

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