SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'b8cd8586fe0147faea145f93c04feadee2355609a88a95d3130e47ae97b8e343' 
  AND token = 'PJhCuGGTkAKegf+sFONTPUi8L0O2lOaxRFkd3kpgA5s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}