PostHog's architecture

graph LR
    u[User]
    sdk[Client Apps/SDKs]
    ex[Export Sink]
    dj[Web/API]
    p[plugin/worker service]
    c[Celery]
    ds[(Data stores)]
    u-->dj
    sdk --> dj
    p --> ex
    dj --> p
    p <--> ds
    dj-->c
    c <--> ds
    dj <--> ds

graph LR
    u[User]
    sdk[Client Apps/SDKs]
    ex[Export Sink]
    ds[(Data stores)]

    subgraph Web/API
        w[Web]
        c[Capture API]
        d[Decide API]
        cr[cron]
        ce[Celery]
    end

    subgraph "plugin/worker service"
        i[Ingestion]
        a[Async]
        t[timer]
    end

    u-->|views insights and more|w
    sdk-->|send events|c
    sdk-->|read|d
    w-->ds
    c-->|write events|i
    i-->|onEvent|a
    i-->|save events|ds
    t-->|onTimer|a
    a-->|export events|ex
    d-->|e.g. read flags|ds
    ds-->|read events|a
    w-->|start task|ce
    cr-->|on schedule|ce
    ce-->ds

flowchart TD
    subgraph K8s ["K8s PostHog namespace"]
        Ingress(Ingress)
        PG[(Postgres Stateful service)]
        Kafka[(Kafka Stateful Service)]

        KafkaEvents[(Kafka Stateful Service)]
        Redis[(Redis SS)]

        ServiceLB([Service Load Balancer])
        ServiceLBReads([Service Load Balancer])

        subgraph ServicesDB [K8s Services]
            PGBouncer
        end

        subgraph CH ["ClickHouse Cluster (Operator Managed)"]
            CH1[(Replica 1 Shard 1)]
            CH2[(Replica 1 Shard 2)]
            CH3[(Replica 2 Shard 1)]
            CH4[(Replica 2 Shard 2)]
        end

        subgraph ZK [K8s ZooKeeper cluster]
            ZK1
            ZK2
            ZK3
        end

        subgraph AppServices [K8s Services]
            Events(Events Service)
            App(Web Service)

            na %% Invisible helper node
        end


        subgraph WorkerServices [K8s Services]
            Plugins[Plugin Service]
            Worker[Worker Service]
        end
    end

    AppServices --> ServiceLB --> ServicesDB --> PG

    Events --> KafkaEvents --> Plugins --> Kafka --Write path--> CH
    WorkerServices --> ServiceLBReads
    WorkerServices --> ServiceLB
    ServiceLBReads --Read path--> CH


    AppServices --> ServiceLBReads

    CH --> ZK

    CH1 <--> CH2
    CH3 <--> CH4

    ClientApps(Client Apps)--- Ingress

    %% KLUDGE: Use invisible nodes for styling purposes
    Ingress --- na[ ]
    na --Other traffic--> App
    na --Events endpoint --> Events
    style na height:0px,width:0px

    Redis -.- WorkerServices
    AppServices -.- Redis

    AppServices-.Optional Utilization telemetry.->Telemetry(Posthog License Telemetry service)

    class K8s,ServicesDB,CH,ZK,AppServices,WorkerServices sgraph;