SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '273aebf8e91a8b917537ca70069cd5c728654c120171bbb36ad467794fcaa312' 
  AND token = 'xiPYmvDlHo+lWhfUFy/FlnGBsx7wAiDjEpDzIMX/dxE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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