5x faster Edge Functions: V8 isolates to Firecracker MicroVMs
Netlify’s move from externally hosted V8 isolates to Firecracker-based MicroVMs at the edge is being used to claim around 5x faster median performance, but many observers note that most of the gain likely comes from eliminating extra network hops rather than the isolation technology itself. The conversation centers on trade-offs between V8 isolates, containers, and microVMs: isolates offer better density and startup times but weaker security boundaries, while microVMs provide stronger kernel-level isolation at the cost of more complexity and overhead. Broader themes include how much isolation is “enough” for different workloads, comparisons with Cloudflare Workers and AWS Lambda, and emerging tools that bring Firecracker-style sandboxing to everyday developers.
Performance claims and where the speedup comes from
- Several commenters argue the 5x improvement is mostly from eliminating a network hop to a third‑party “hosted execution service,” not from switching V8 isolates → Firecracker per se.
- Old setup: requests left Netlify’s network to another provider (apparently Deno) then came back.
- New setup: microVMs run inside Netlify’s own edge network, so latency is dominated by local routing.
- Some see the title as slightly misleading because it frames the gain as “isolates vs microVMs” rather than “remote vs in‑network execution.”
V8 isolates vs microVMs: security and isolation
- Isolates are described as sharing process, address space, memory allocator, and kernel; they’re considered weaker isolation than microVMs.
- V8’s JIT complexity and historical bugs raise concerns about sandbox escapes; some note that the V8 team doesn’t treat isolates as a strong security boundary.
- MicroVMs provide separate kernels and hardware virtualization, but are still weaker than giving each tenant a dedicated machine.
- Some argue isolates are “good enough” for many non‑security‑critical or same‑customer workloads and give better resource utilization.
- Others insist kernel-level isolation is preferable and note Chrome itself does not trust isolates alone.
- Snapshotting microVMs raises RNG/UUID/crypto concerns; Firecracker has documented mitigations, but there’s precedent for getting this wrong in similar systems.
Comparisons to Cloudflare Workers and AWS Lambda
- Commenters puzzled that Netlify’s previous isolate-based system had 25–40 ms overhead while Cloudflare Workers (also V8 isolates) are much faster; network topology differences are cited as the main reason.
- Netlify’s reported ~15 ms warm / ~25 ms cold is contrasted with much slower Lambda cold starts; people blame Lambda’s “enterprisey extras” rather than Firecracker itself.
MicroVMs, containers, and tooling
- Debate over whether Firecracker will “replace Docker”: consensus leans no, because containers share a kernel and are more resource-efficient, though microVMs are attractive for stronger isolation.
- MicroVM projects like Unikraft, SlicerVM, and smolvm are discussed; they’re praised for performance and security, but also critiqued for pricing, UX, or security posture vs Firecracker.
Edge runtimes, JavaScript, and standards
- Some question using JavaScript when counting milliseconds; others respond that V8 is highly optimized for startup.
- A request is made for Netlify Edge Functions to support a Fetch-like standard interface (Fetchable) to improve portability across runtimes.