SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a31c71a3cf384a5154ba3847ddd4aac9de286834717893981502b8d0269e9feb' 
  AND token = 'sXCYRukkgkEfPjMdVZxk1ZeWClrkfzXYV7o8obaK9LM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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