Addressr vs a hosted G-NAF API: when to self-host

5 Sept 2026 · 6 min read

Addressr is an open-source project, maintained by Mountain Pass under its own licence, that ingests the quarterly G-NAF release into OpenSearch and exposes an address autocomplete API. It is good software. It is the engine under WattleAddr’s API, and WattleAddr runs it but is not its author. This post is about which parts of the job you want to own.

What self-hosting Addressr involves

• A box with enough memory for an OpenSearch index of roughly 17 million address records, and an OpenSearch version its Elasticsearch client supports (WattleAddr runs 1.3.20; 2.x is incompatible).
• A quarterly ingest of a multi-gigabyte G-NAF release, ideally with zero downtime, and a check that the new index answers before you switch to it.
• Rate limiting, API keys, per-key domain locks and usage metering, none of which are the engine’s job.
• Query relaxation for misspelt suburbs and dropped street types. Most accuracy work sits here, and WattleAddr adds it on top of the engine.
• PO Box detection, so a postal query returns a useful message instead of a wrong street. WattleAddr also adds this in front of the engine.
• Monitoring, backups, a standby, and someone awake when the index stops answering.

None of that is hard for a team that runs OpenSearch already. All of it is a distraction for a team that does not.

When to self-host

• You already operate OpenSearch or Elasticsearch in production and have the people on call for it.
• Your volume is large enough that per-lookup pricing exceeds a box plus an engineer-day a quarter.
• You need a customisation the API does not expose, such as a private dataset merged into the index.
• Your data-residency rules require the index inside your own network rather than in an Australian provider’s.

When to use the hosted API

• You want autocomplete on a form this week, not a platform this quarter.
• You want verification with a verdict and per-field status, not only autocomplete.
• Your volume is in the thousands to low millions of lookups a month, where the plans are cheaper than the box.
• You want the G-NAF refresh, the relaxation logic, the PO Box handling and the monitoring to be someone else’s problem, in Australia.

What WattleAddr adds on top of the engine

The parts listed above: a daily check for new G-NAF releases with an in-place refresh, query relaxation measured against a published benchmark, an explicit notice for postal addresses, keys with domain and IP locks, session-based metering so autocomplete keystrokes are not billed, the verify endpoint, a Sydney primary with a Melbourne standby, and a published data-residency attestation. If you self-host Addressr, you will build some of that list yourself.