How to tune ID generation

Two settings change how IDs are minted without changing what a call site asks for: monotonic generation, for bursts of IDs in one millisecond, and a size floor, for test suites that mint small IDs quickly. Why monotonic mode exists and what it costs is on Why monotonic mode exists and what it costs; every key below is listed in the Configuration reference.

Turn on monotonic generation

Per call, for every size or for a list of sizes:

# Per-call: on for all sizes
UXID.generate!(size: :small, monotonic: true)

# Per-size list (alias-aware: :small also matches :s, :medium matches :m, ...)
UXID.generate!(size: :small, monotonic: [:small, :medium])

Global policy (overridable per-call/per-field, mirrors compact_small_times):

# config/config.exs
config :uxid, monotonic: true
# or only for specific sizes:
config :uxid, monotonic: [:small, :medium]

In Ecto schemas:

field :id, UXID, autogenerate: true, prefix: "evt", size: :small, monotonic: true

On a registry key - declare it once and both generate!/2 and field_opts/1 carry it, so no call site or schema field can disagree (see How to govern prefixes with a registry):

defid :event, prefix: "evt", size: :small, monotonic: true

MyApp.IDs.generate!(:event)                   # monotonic
MyApp.IDs.generate!(:event, monotonic: false) # one-off opt-out

Enforce a minimum size in tests

In test environments, code that requests :small (or smaller) can generate enough IDs to hit duplicate-key violations. The :min_size config upgrades any requested size below the floor, without touching larger ones:

# config/test.exs
config :uxid, min_size: :medium

See the Configuration guide for details.