How Developers Use Government Data APIs in Production Applications

The Appeal and the Reality of Government APIs

Government data APIs are appealing because the data is authoritative, free, and comprehensive. The reality is that they are also often poorly documented, have inconsistent data quality, have strict rate limits, and change without notice. Building production systems on top of government APIs requires defensive engineering.

Companies House API: Production Considerations

Key production considerations: rate limits (600 requests per 5 minutes per API key), pagination (advanced search returns 100 results per request with start_index parameter), data freshness (new registrations appear within a few days), authentication (HTTP Basic Auth with API key as username, empty password), and bulk data alternative (use bulk data product for more than 50,000 records).

NPPES: Working With the Bulk Download

NPPES does not offer a proper REST API — the primary access method is the monthly full data dissemination file: a ZIP archive containing large CSV files (typically 6–8 GB uncompressed). Processing it efficiently requires streaming decompression, chunked reading (pandas chunksize parameter), and indexing on NPI number and state after import.

When to Use Pre-Packaged Data Instead of APIs

Use pre-packaged datasets when you need a complete snapshot, when your application needs the data as a lookup table (pre-import into your database once per month), when building a non-technical workflow (CRM import), or when you want to avoid building and maintaining parsing logic for government data formats that change without notice.