I just noticed on the Jolokia website that it was tested with 500 servers monitored by Nagios and it was said that Jolokia scales nicely with 10 parameters requests every 5 minutes. I planned to collect metrics every 10 seconds. Will Jolokia fit this purpose (I have strict low-latency requirements for my app) or I need to consider not to use JMX at all?
It depends on how many metrics you want to request regularly. The most expensive thing is the JSON serialization (+ of course the time the JMX operation itself needs, but that's nothing Jolokia can influence).
For the client fetching the metrics it shouldn't be a problem, however the load on the system monitored might increase (remember, from the 500 servers each is requested only once per 5 minutes, so 60times less).
Yet an alternative could be monitoring with Prometheus and the collector jmx_exporter which doesn't use JSON (but might have other issues). Prometheus is supposed to monitor also in quite small intervals (15s by default).