### ingestion_materialization

```{eval-rst}
.. plantuml::

   @startuml
   ' Explicitly enforce sequence diagram
   !define RECTANGLE class
   skinparam monochrome true
   skinparam shadowing false
   title Ingestion & Materialization Sequence
   !pragma layout smetana
   ' top to bottom direction
   
   actor Producer as P
   participant "X2 Gateway" as GW
   participant "X2 Sequencer" as SQ
   participant "X2 Storage" as ST
   participant "X2 Materializer" as MAT
   participant "CH Kafka Engine Table" as CHK
   database "CH MergeTree\n(ReplacingMergeTree x2_seq)" as CHMT
   database "Iceberg on S3/MinIO" as ICE
   participant "CH Iceberg Reader" as CHI
   
   P -> GW: Kafka Produce (records)
   GW -> SQ: Append (records)
   SQ -> ST: Persist + Replicate
   ST -> CHK: Stream (Kafka pull)
   CHK -> CHMT: MV INSERT (dedupe by x2_seq)
   
   ST -> MAT: Notify window/watermark
   MAT -> ICE: Write snapshot + manifests
   
   CHI -> ICE: SELECT ... (historical)
   
   @enduml