What is a noisy neighbor?
A noisy neighbor is another tenant on shared hardware whose heavy use of CPU, memory, disk or network slows your workload down.
On Runtime every sandbox has a guaranteed CPU floor, its own memory, a fair share of the disk and network limits, all enforced on the host outside the guest. Its disk gets at least about 40 MB/s however busy its neighbours are, and up to about 1 GB/s when they are not, so one busy sandbox cannot starve the others on its server (the sandbox environment).
Where the term comes from
Microsoft's Azure Architecture Center describes it as an antipattern of multitenant systems: the problem "occurs when one tenant's performance is degraded because of the activities of another tenant". It can happen when one tenant uses a disproportionate share, or when many small tenants peak at once. From the outside it looks like a request that succeeds most of the time and fails, or slows, at random.
What a neighbor can take from you
| Shared resource | What goes wrong | How a platform limits it |
|---|---|---|
| CPU time | Your threads wait for a core | A guaranteed share per tenant, capped bursts |
| A core's two threads | Cache and execution units are contested | Core scheduling keeps strangers off one core |
| Memory | The host swaps or kills processes | Fixed memory per tenant |
| Disk I/O | Latency spikes behind someone's writes | A rate limit with a burst allowance |
| Network | Throughput drops | Per-tenant bandwidth caps |
The Linux kernel's documentation describes core scheduling as letting userspace "define groups of tasks that can share a core", so that "only trusted tasks" run side by side on the two threads of one core.
The Runtime answer, in numbers
- CPU: a floor of a twentieth of a vCPU by default, raised with
cpuFloorMillis, or every vCPU reserved withcpu: "reserved"(shared vs reserved CPU). - Memory: what the sandbox asks for, up to 64 GiB on a paid one.
- Disk: the host's kernel divides the drives between busy sandboxes in proportion and holds every read and write near a latency target, so a heavy writer next door slows your writes a little and never stops them.
- Network: a paid sandbox moves up to 500 GiB a day (pricing).
Related
Sources
Checked 27 September 2026.