digraph techviz {
  graph [rankdir=TB, splines=ortho, nodesep=0.55, ranksep=0.85];
  node [fontname=Helvetica, fontsize=11, margin="0.18,0.12", style="rounded,filled", fillcolor=white, color="#2d4357", penwidth=1.5];
  edge [fontname=Helvetica, fontsize=10, color="#364b5f", penwidth=1.4, arrowsize=0.75];
  subgraph cluster_0 {
    label="Guest Userspace";
    style="rounded,dashed";
    color="#66788a";
    n0 [label="PostgreSQL / Keycloak", shape=box, style="rounded,filled"];
  }
  subgraph cluster_1 {
    label="Guest Kernel";
    style="rounded,dashed";
    color="#66788a";
    n1 [label="VFS", shape=box, style="rounded,filled"];
    n2 [label="ext4 / XFS", shape=box, style="rounded,filled"];
    n3 [label="Guest Page Cache", shape=box, style="rounded,filled"];
    n4 [label="Guest Block Layer", shape=box, style="rounded,filled"];
    n5 [label="/dev/vda", shape=box, style="rounded,filled"];
    n6 [label="virtio-blk Frontend", shape=box, style="rounded,filled"];
    n7 [label="virtqueue", shape=oval, style="rounded,filled"];
  }
  n0 -> n1 [label="", style=solid];
  n1 -> n2 [label="", style=solid];
  n2 -> n3 [label="", style=solid];
  n3 -> n4 [label="writeback", style=solid];
  n4 -> n5 [label="WRITE / FLUSH", style=solid];
  n5 -> n6 [label="", style=solid];
  n6 -> n7 [label="Virtio block request", style=solid];
}