---
url: /logly.zig/examples/sampling-key.md
description: >-
  Deterministic per-key sampling with Logly.zig so the same IDs always sample
  the same way.
---

# Key-Based Sampling

`shouldSampleKey` hashes the key, so `user-123` always gets the same decision.

```zig
var sampler = logly.Sampler.init(allocator, .{ .probability = 0.2 });
defer sampler.deinit();

for (users) |user| {
    if (sampler.shouldSampleKey(user)) {
        try logger.info("sampled", @src());
    }
}
```

Output:

```text
user-123: skip
user-456: skip
user-789: skip
```