3D Mobile Offline Write-Queue Relay Simulator

Queue a write (local)

Connectivity

Simulate an out-of-band write

Conflict policy on drain

Queue length

Edge / Origin v

0 / 0

Applied in order

Conflicts hit

Queue log

Ready. Go offline, queue a few writes, then reconnect.

How it works

This is the two-hop version of the offline write queue: a mobile device drains its local FIFO queue through an edge cache first, then the edge forwards to the origin server — two independently versioned nodes instead of one.

for op in queue (in order):
  if edge.version != op.baseVersion: CONFLICT at EDGE
  else: provisionally apply at edge, edge.version++
        if origin.version != op.baseVersion: CONFLICT at ORIGIN (edge already moved on!)
        else: apply at origin, origin.version++

Two independent checkpoints — the 2D single-hop version only ever checks the op against one server. Here an op can pass the edge check yet still collide at the origin, because someone wrote to the origin directly and bypassed the edge cache entirely — a real CDN/edge-cache staleness scenario.
"Write @ Edge" vs "Write @ Origin" — the two out-of-band buttons let the two tiers drift apart on purpose, which the single-hop 2D model has no equivalent of.
Abort / Skip / Force — same three policies as the 2D queue, but now applied at whichever hop actually failed.
Rebase & retry — resyncs every remaining queued op's base version to the edge's current version and resumes.

Real-world relevance: mobile apps behind a CDN/edge layer (Cloudflare Workers KV, a regional cache in front of an API) face exactly this — a write can be acknowledged at the edge before the origin has actually seen it, and the two can disagree.

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