Backpressure in Real-Time Blockchain Data Consumers
Bound queues and consumer concurrency when event arrival exceeds processing capacity, while preserving durable progress and explicit overload behaviour.
Overview
When translating these concepts into an integration, keep the scope described by the wallet history api with the result. The examples in wallet transaction history and smart contract event logs show how the same distinction affects neighbouring data questions.
A consumer that accepts events faster than it can process them eventually runs out of memory or loses control of latency. Backpressure makes that limit visible and actionable.
Bound every stage
Set limits for in-memory queues, concurrent work and pending writes. Measure input rate, processing rate and oldest-unprocessed age. A fast network receiver can conceal a slow database. Decide whether the delivery protocol can pause, retry or persist work elsewhere; do not assume unlimited buffering is a safe fallback.
Worked example: a burst exceeds capacity
Events arrive at one thousand per second while the consumer can durably process two hundred. An unbounded queue grows by eight hundred each second. A bounded design slows intake where supported or acknowledges only after durable handoff, then recovers the remaining range under the delivery contract.
Preserve overload semantics
Test sustained overload, process restart and a downstream write outage. Do not acknowledge and discard work merely to keep the endpoint responsive. Keep per-event identities so replay is safe. Alert on lag as well as error rate: a consumer can return successful acknowledgements while falling farther behind useful coverage.
A practical acceptance test
Generate a bounded burst above the consumer’s processing rate and inspect queue length, oldest-item age and durable handoff. Assert the chosen overload behaviour before memory grows without limit. Stop the downstream writer and restart the consumer. Accepted acknowledgements must correspond to the declared durable boundary, while unprocessed work remains recoverable under the delivery contract.
Questions about the topic
Frequently asked questions
Can a successful receiver still be unhealthy?
Yes. Its queue and coverage lag can grow despite successful HTTP responses.
Is an unbounded queue a recovery strategy?
No. It eventually exhausts resources and obscures completion.
Standards & technical documentation
