Zcash NU7 Explained: 25-Second Blocks and Gemini's Move to Zakura

Gemini, one of the larger regulated crypto exchanges in the US, has rebuilt part of its Zcash infrastructure. It moved its Zcash nodes to new software called Zakura, and it gave a specific reason: Zcash is preparing to cut its target block time from about 75 seconds to about 25 seconds.

That change is part of NU7, Zcash’s next network upgrade, and it now has a public calendar. This article covers what Gemini changed, what NU7 does and doesn’t do, and the dates holders can track.

What did Gemini change?

Gemini moved its Zcash infrastructure from software based on Zebra to Zakura, an open-source Zcash full node written in Rust.

A full node is software that downloads blocks, verifies transactions, checks the network’s rules and talks to other nodes. Gemini needs this to support ZEC deposits and withdrawals. According to Gemini, Zakura is consensus-compatible with Zcash, is based on a fork of Zebra, and is designed for faster synchronization, storage efficiency, pruning and faster recovery.

The performance claims cited in the video:

Measure	Zakura	Zebra
Full sync, Zakura’s published benchmarks	about 4 hours 20 minutes	nearly 21 hours
Reaching the chain tip, Gemini’s own deployment	a little over 6 hours	close to a full day

Zakura also publishes pruned snapshots of roughly 12 GB. A new server can start from one instead of rebuilding the whole history from other nodes. Gemini quoted a roughly 680-times improvement in startup for that particular process.

Does this make ZEC transactions faster?

Not on its own. These numbers are about how fast a node syncs and recovers, not how fast a payment arrives. Gemini says customer deposits and withdrawals should continue working as before.

The improvement matters for reliability. If a node fails, an exchange doesn’t want to spend a day waiting for it to catch up. The video’s point is that this kind of plumbing is what adoption usually depends on.

What is NU7?

NU7 stands for Network Upgrade 7. Its best-known proposed change, set out in a Zcash improvement proposal called ZIP 218, is shorter blocks:

• Today the target block spacing is about 75 seconds.
• ZIP 218 proposes about 25 seconds.

The main reason is user experience. ZIP 218 says the change can produce roughly a three-times reduction in waiting time for users who need one or two confirmations. That is a target spacing, not a guarantee that every transaction is final in 25 seconds, and services can require different numbers of confirmations.

ZIP 218 also adjusts limits in Zcash’s shielded pools. According to the proposal, under its stated assumptions, throughput in the Orchard shielded pool would rise from roughly 2.9 to 6.6 transactions per second. Scaling private transactions is harder than scaling public ones, because privacy adds computation and data.

The ecosystem timeline also lists disabling version 4 transactions and adding a network sustainability mechanism based on selected proposals.

Why Gemini prepared before the upgrade

Going from 75-second to 25-second blocks means nodes handle about three times as many blocks over the same period. That affects syncing, storage, indexing, recovery and reliability. Gemini’s statement says the extra workload is why sync speed, storage efficiency and recovery time matter more now.

Gemini has a long record with Zcash. It says it first listed ZEC in 2018, added shielded withdrawals in 2020, and later added unified addresses and Orchard support. The video reads the Zakura move as Gemini continuing to invest in Zcash infrastructure, while stressing that this is support for customers using the network, not Gemini buying ZEC as an investment.

What NU7 does not do

Crypto narratives tend to stretch upgrades, so the video was specific about the limits:

• NU7 does not create a new maximum supply for ZEC.
• Faster blocks do not mean three times as much ZEC is created per day. ZIP 218 adjusts block rewards for the shorter interval so the issuance schedule stays consistent in ZEC per day.
• A faster network does not guarantee a higher price, and it doesn’t remove the regulatory pressure privacy coins face.

Privacy and the regulation question

Zcash’s core feature is optional financial privacy. Shielded transactions use zero-knowledge cryptography, which lets the network verify a transaction without publicly exposing all of its details. Bitcoin and Ethereum, by contrast, are public by default.

The video argues that privacy becomes more relevant as finance moves on-chain. Businesses may not want payroll, supplier payments or treasury moves permanently visible. But privacy coins have also faced exchange restrictions, delistings and regulatory scrutiny. Zcash is trying to offer real privacy while staying usable by regulated firms, which is why a US-regulated exchange investing in its infrastructure is notable.

The NU7 timeline

The published schedule, as cited in the video:

1. September 30, 2026: code completion target.
2. October 6: testnet upgrade.
3. October 20: final mainnet activation decision and height, based partly on testnet experience.
4. November 5: mainnet target.

Five things to watch

The video’s own checklist for tracking whether NU7 matters:

1. October 6: does NU7 activate successfully on testnet?
2. October 20: does the ecosystem confirm the mainnet activation, or do problems push it back?
3. November 5: does NU7 go live as planned, and how does the network behave afterwards?
4. Exchanges: Gemini is ready. Do Coinbase, Kraken and other major platforms upgrade too?
5. Shielded usage: does a better user experience lead to more people actually using Zcash’s privacy features?

The last one is the measure the video cares about most. A technically better network isn’t automatically a more valuable one. Zcash still needs users, liquidity, wallet and exchange support, developers and real reasons for people to choose private transactions. Attention around a coin fades; the video’s argument is that infrastructure and usage are the parts worth tracking.