GravityKit
GravityKit ships weekly across a whole plugin suite, with an MCP server now part of the lineup.
Comparison · Infra & APIs
Firecracker vs Knock
A side-by-side editorial comparison of Firecracker and Knock — release velocity, themes, recent moves, and the top alternatives to consider.
Firecracker vs Knock: at a glance
| Feature | Firecracker | Knock |
|---|---|---|
| Sector | Infra & APIs | Infra & APIs |
| Velocity score | 0.0 | 6.3 |
| Sparks · 30d | 0 | 1 |
| Top themes | microvm, device hotplug, snapshots, pci transport | notification-infrastructure, data-sources, agent-native, workflow-orchestration |
| Last editorial update | 2h ago | 11h ago |
| Website | Visit → | — |
What is Firecracker?
Firecracker's microVMs can now grow and shrink devices while running.
1.16.0 in June added developer-preview hotplug and hot-unplug for PCI virtio block, pmem and net devices on a live microVM, with the guest responsible for rescanning the bus and removing the device first since no notification mechanism exists yet. The same release added vsock Unix socket path overriding on snapshot restore, rate limiting for serial console output with a dropped-bytes metric, and per-callsite log rate limiting. 1.16.1 followed with a vsock fix for connections timing out after restore when a snapshot caught an in-flight TX descriptor. Earlier in the window, 1.15.0 added the VMClock device and Intel Granite Rapids support, and the April patches hardened the PCI transport against CVE-2026-5747.
What is Knock?
Knock is wiring both ends of the messaging data loop, then putting an agent on top
Knock has spent the last month building around its notification engine rather than inside it. Two new inbound data sources, Amplitude and Clay, let product events, cohorts, and enriched account rows land in Knock without customers writing sync code, while message and engagement events flow back out to the warehouse. The dashboard work alongside it, a rebuilt template editor, saved views and tags, schema management, and passkeys, reads as hardening for teams rather than individual developers.
Firecracker vs Knock: editorial side-by-side
Firecracker
0.0INFRA · APIS
Firecracker's microVMs can now grow and shrink devices while running.
◆ Current state
1.16.0 in June added developer-preview hotplug and hot-unplug for PCI virtio block, pmem and net devices on a live microVM, with the guest responsible for rescanning the bus and removing the device first since no notification mechanism exists yet. The same release added vsock Unix socket path overriding on snapshot restore, rate limiting for serial console output with a dropped-bytes metric, and per-callsite log rate limiting. 1.16.1 followed with a vsock fix for connections timing out after restore when a snapshot caught an in-flight TX descriptor. Earlier in the window, 1.15.0 added the VMClock device and Intel Granite Rapids support, and the April patches hardened the PCI transport against CVE-2026-5747.
◆ Where it's heading
The through-line is snapshots and the PCI transport maturing together. Firecracker's value has always been fast boot from a snapshot, and the recent fixes are all in the seams that opens up — TX descriptors in flight when a snapshot is taken, vsock paths that change on restore, virtio device state machines that must be validated the same way on PCI as on MMIO. Hotplug extends the same idea from restore-time to run-time: a microVM that can change shape is one you can keep rather than replace.
◆ Prediction
Hotplug shipped explicitly as a developer preview requiring manual guest bus rescans, so the stated gap is an automatic notification mechanism. That is the obvious next step before the feature leaves preview.
Knock
6.3INFRA · APIS
Knock is wiring both ends of the messaging data loop, then putting an agent on top
◆ Current state
Knock has spent the last month building around its notification engine rather than inside it. Two new inbound data sources, Amplitude and Clay, let product events, cohorts, and enriched account rows land in Knock without customers writing sync code, while message and engagement events flow back out to the warehouse. The dashboard work alongside it, a rebuilt template editor, saved views and tags, schema management, and passkeys, reads as hardening for teams rather than individual developers.
◆ Where it's heading
The direction is away from a notification API you call and toward the system that holds the messaging state. Ingesting cohort membership and enriched contact data is CDP-adjacent territory, and the wait-for-event function turns linear sequences into event-driven orchestration. The Knock agent then adds a natural-language layer over performance data, so the platform answers questions instead of only exporting rows.
◆ Prediction
Expect more data sources on the same pattern, warehouse and CRM-side connectors that keep audiences in sync without customer glue code. Whether the agent moves from reading analytics to editing workflows directly is the open question these entries do not yet answer.
Alternatives to Firecracker and Knock
Other Infra & APIs products tracked by Sparkpulse, ranked by recent ship velocity. Each card links to a full editorial trajectory and lets you pivot into a head-to-head comparison with either Firecracker or Knock.
LibreSpeed
After a two-year redesign, LibreSpeed is adding tests instead of polishing pixels.
Nautobot
A security advisory cycle forced Nautobot to break its REST API on both supported branches at once.
Gatekeeper
Gatekeeper grew a package manager for policies — and a benchmark to prove they are not too slow.
GoCD
GoCD's changelog is one maintainer keeping a 2010s CI server running on current runtimes.
Incus
Incus settled its 7.0 LTS, then went straight back to a monthly feature cadence.
See all Firecracker alternatives → · See all Knock alternatives →
Recent activity from Firecracker and Knock
Latest ship moves from both products, interleaved chronologically. ⚡ = editorial spark.
- 1d agoKnockAmplitude data source
- 8d agoKnockAnalytics in the Knock agent ⚡
- 9d agoKnockWait for event function
- 10d agoKnockClay data source
- 15d agoKnockRedesigned template editor
- 22d agoKnockBranch rebasing
- 1mo agoFirecrackerVsock timeout after snapshot restore, and jailer symlink revert
- 2mo agoFirecrackerFirecracker v1.16.0 ⚡
- 4mo agoFirecrackervirtio-rng entropy cap and PCI transport hardening (CVE-2026-5747)
- 4mo agoFirecrackerCVE-2026-5747 hardening on the 1.15 branch
- 4mo agoFirecrackerTCP SYN options length validation with MMDS enabled
- 5mo agoFirecrackerVMClock device and Intel Granite Rapids support
Frequently asked questions
What is the difference between Firecracker and Knock?
They serve adjacent needs but don't currently overlap on shipped themes. Knock is currently shipping more aggressively (velocity 6.3 vs 0.0), with 1 editorial sparks in the last 30 days against 0. See the at-a-glance table above for a side-by-side breakdown of velocity, recent sparks, and editorial themes.
Is Firecracker better than Knock?
Sparkpulse doesn't pick a winner — we score release velocity, not feature parity. Knock is currently shipping more aggressively (velocity 6.3 vs 0.0), with 1 editorial sparks in the last 30 days against 0. For your specific use case, the alternatives sections above list other Infra & APIs products to evaluate alongside.
What are the best alternatives to Firecracker?
Top Firecracker alternatives in Infra & APIs are ranked by recent ship velocity. Browse the "Firecracker alternatives" section above for the current picks, or visit /alternatives/firecracker for the full list with editorial commentary on each.
What are the best alternatives to Knock?
Top Knock alternatives in Infra & APIs are ranked by recent ship velocity. Browse the "Knock alternatives" section above for the current picks, or visit /alternatives/knock for the full list with editorial commentary on each.