posthog-observability

# PostHog Observability ## Overview Monitor PostHog integration health with four key signals: event ingestion rate (are events flowing?), feature flag evaluation latency (are flags fast enough for hot paths?), event volume by type (detect instrumentation regressions), and API rate limit consumption (are we approaching 429s?). ## Prerequisites - PostHog project with personal API key (`phx_...`) - Application instrumented with PostHog SDK - Prometheus/Grafana or equivalent monitoring stack (optional) ## Instructions ### Step 1: Event Ingestion Health Check ```bash set -euo pipefail # Check if events are flowing (last 24 hours) curl "https://app.posthog.com/api/projects/$POSTHOG_PROJECT_ID/query/" \ -H "Authorization: Bearer $POSTHOG_PERSONAL_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "query": { "kind": "HogQLQuery", "query": "SELECT toStartOfHour(timestamp) AS hour, count() AS events FROM events WHERE timestamp > now() - interval 24 hour GROUP BY hour ORDER BY hour" } }' | jq '.results | map({hour: .[0], events: .[1]}) | .[-3:]' ``` ### Step 2: Instrument Flag Evaluation Latency ```typescript // posthog-instrumented.ts import { PostHog } from 'posthog-node'; const posthog = new PostHog(process.env.NEXT_PUBLIC_POSTHOG_KEY!, { host: 'https://us.i.posthog.com', personalApiKey: process.env.POSTHOG_PERSONAL_API_KEY, }); // Wrap flag evaluation with timing async function getFlag(flagKey: string, userId: string): Promise<any> { ...