For small apps I would use Monit to watch the server processes combined with CloudWatch to watch the servers themselves.
I would investigate the TICK stack (influxdb) before ELK. TICK is great for metrics that are not stored in log files. tail + awk should be enough for managing log files if you only have a few servers.
I would investigate the TICK stack (influxdb) before ELK. TICK is great for metrics that are not stored in log files. tail + awk should be enough for managing log files if you only have a few servers.