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Snapshots, forking and cold starts

Restoring a snapshot instead of booting from scratch is how a microVM starts in milliseconds, and copy-on-write is how one running machine becomes many. These posts cover snapshot-restore internals, forking a live VM, hibernation and scale-to-zero, and what those primitives enable for agents and tests.

Thaw: sub-second cold restore

97 posts

·10 min read

Distributed Data Processing on Ephemeral MicroVM Fleets

Fork sixty-four workers from one parent that has already resolved the dependency closure, and they will be running in under a second. Ask any two of them to exchange a shuffle block and the host firewall will drop the packet, by design.

distributed-computingdata-processingspark
Ajay Kumar
·11 min read

The Carbon and Energy Case for Scale-to-Zero Compute

The sustainability argument for scale-to-zero is not that your code got efficient. It is that the machine can be handed to somebody else. Which only counts if somebody actually takes it.

scale-to-zerodensityenergy
Ajay Kumar
·9 min read

Snapshot the Failure, Not the Log Line

The expensive part of an intermittent bug is not the analysis. It is getting back to the failing state. A log line is a guess someone made in advance about what would matter; a memory snapshot is the state itself.

debuggingflaky-testssnapshots
Ajay Kumar
·10 min read

Running EDA and Chip-Design Workloads in MicroVMs

In most workloads the compute is worth more than the data. In chip design it is emphatically the other way round: a netlist or a foundry PDK leaking to a co-tenant is a company-ending event, and the NDA you signed has opinions about which kernel your job shares.

edachip-designmicrovm
Ajay Kumar
·10 min read

How to Put a CDN in Front of a Scale-to-Zero App

An origin that is allowed to sleep changes what your cache headers are for. Done properly, the wake happens in a background fetch and lands on nobody's request; done carelessly, one Vary header hands every visitor a cold boot.

cdncachingscale-to-zero
Ajay Kumar
·11 min read

virtiofs vs virtio-blk: How Files Actually Get Into a MicroVM

One gives the guest a disk it owns. The other gives it a window onto a directory the host owns. That single difference decides whether you can fork a machine in 400ms, who parses guest-controlled input, and what a multi-tenant escape looks like.

virtiofsvirtio-blkfirecracker
Ajay Kumar
·11 min read

Why the disk under your sandbox fleet decides your boot time

People pick a sandbox platform on features and then get bitten by storage hardware. A reflink clone is metadata-only and nearly free; every copy-on-write byte afterwards is a real read-modify-write against a real device. Under 50 concurrent restores, that device is either local NVMe or it is your bottleneck.

storagenvmecopy-on-write
Ajay Kumar
·10 min read

Golden Images vs Snapshot Baking

A golden image removes install time. A snapshot removes boot time. Those are different costs, which is why the answer is almost always both — and why the snapshot quietly freezes your RNG, your clock, and anything that was in RAM at bake time.

golden-imagessnapshotsfirecracker
Ajay Kumar
·10 min read

Per-Tenant SQLite: One File, One microVM, and No Noisy Neighbours

One SQLite file per customer gets the data model right: blast radius is a path, erasure is rm. Then you put a thousand of them in one process and discover that a file boundary is not a failure boundary.

sqlitemulti-tenancymicrovm
Ajay Kumar

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