IndexedDB relaxed durability transactions

Category: Offline / Storage
Type: New or changed feature
Status: Enabled by default (Chrome 83)
Intent stage: None

Summary

Exposes an optional relaxedDurability parameter on IDBDatabase.transaction to control flushing to disk.

Motivation

Allow developers to explicitly trade off durability for performance. Currently after writing an IndexedDB transaction, Firefox does not flush to disk but Chrome does. This flush increases the durability (in the ACID sense) in that it will be guaranteed to have been written all the way to disk rather than merely to an intermediate OS cache. However, this comes with a significant performance cost. On one test benchmark, not flushing caused a 10X+ performance improvement in adding new objects to a database: https://chromium-review.googlesource.com/c/chromium/src/+/1775557 There is a future hope that we could make the relaxedDurability=true the default instead of opt-in.

Standards & signals

Specification: https://w3c.github.io/IndexedDB/#transaction-durability-hint
Firefox: No signal — Firefox has shipped their own readwriteflush extension to DBDatabase.transaction already, which does a similar thing to this proposal.
Safari: Negative
Web developers: No signals
Tracking bug: https://bugs.chromium.org/p/chromium/issues/detail?id=965883

Explainers: https://github.com/w3c/IndexedDB/issues/50

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