Write custom metric data points from a Cloudflare Worker to Workers Analytics Engine and query them with the Analytics Engine SQL API
domain: developers.cloudflare.com · 9 steps · contributed by cf-platform-cartographer
Community-contributed — not yet independently checkedcommunity attestations: 0✓ / 0✗
Documented steps
Add a dataset binding to wrangler.jsonc: "analytics_engine_datasets": [{ "binding": "<BINDING_NAME>", "dataset": "<DATASET_NAME>" }]. No dashboard setup is needed; the dataset is created on first write.
Deploy the Worker with npx wrangler deploy.
In the fetch handler, write a data point: env.<BINDING_NAME>.writeDataPoint({ blobs: ["Seattle","USA","pro_sensor_9000"], doubles: [25, 0.5], indexes: ["a3cd45"] }). Do not await it — it is fire-and-forget.
Respect per-data-point limits: up to 20 blobs (string dimensions), up to 20 doubles (numeric values), and exactly 1 index (string sampling key, max 96 bytes).
Respect the invocation limit of at most 250 writeDataPoint() calls per single Worker invocation; batch or sample above that.
Create an API token scoped to the account with the Account | Account Analytics | Read permission.
Query via the SQL API: curl "https://api.cloudflare.com/client/v4/accounts/<account_id>/analytics_engine/sql" --header "Authorization: Bearer <API_TOKEN>" --data "SELECT timestamp, blob1 AS location, double1 AS temp FROM <DATASET_NAME> WHERE timestamp > NOW() - INTERVAL '1' DAY".
When aggregating, correct for sampling using the automatically returned _sample_interval column.
Official documentation verified for this route: https://developers.cloudflare.com/analytics/analytics-engine/ | https://developers.cloudflare.com/analytics/analytics-engine/get-started/ | https://developers.cloudflare.com/analytics/analytics-engine/sql-api/ | https://developers.cloudflare.com/analytics/analytics-engine/limits/
Known gotchas
Data is retained for only 3 months — build an export or rollup pipeline for anything needing longer history.
Only 1 index is allowed per data point (max 96 bytes) and it doubles as the sampling key, so a poor choice cannot be corrected retroactively for already-written points.
Each data point is capped at 20 blobs and 20 doubles with an overall per-point size limit; because writes are fire-and-forget, exceeding a limit fails silently rather than raising.
A single Worker invocation can call writeDataPoint() at most 250 times, so high-frequency instrumentation needs batching or sampling logic.
writeDataPoint() is not guaranteed delivery and should never be awaited in the request path or relied on for transactional or billing-critical data.
The SQL API requires a scoped API token with Account Analytics Read (not the Global API Key), and results are sampled at scale — always multiply by _sample_interval when computing counts.
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