Breaking Down Zcash's Scaling Roadmap: How 5 Major Technical Upgrades Propel It Toward Becoming a High-Concurrency Privacy Coin?

Author: William M. Peaster (Senior Analyst at Bankless)

Translated by: TechFlow

TechFlow Highlights: In the long evolution of public chains, scalability has always been the elusive technical holy grail for privacy blockchains. With the explosive iteration of on-chain analytics tools and AI tracking technologies, user funds and transaction privacy on fully transparent ledgers have been completely eroded. However, native zero-knowledge privacy computing has long been trapped in throughput bottlenecks due to the heavy burden of full-node verification and state bloat.

In the lead-up to the milestone NU7 network upgrade coming this week (November 5-6), Zcash co-founder Sean Bowe and core protocol contributor Dev Ojha have outlined their comprehensive two-year systematic scaling roadmap. They plan not only to drastically reduce the block time from 75 seconds to 25 seconds but also to leverage homomorphic encryption-based Private Information Retrieval (PIR) enabled by cheaper AI compute power, Tachyon recursive proof aggregation, and stateless node compression to challenge the high-concurrency goal of 50,000 TPS.

From the shorter block times officially rolling out this week to the whiteboard-stage concept of a private RPC payment system, here is the complete roadmap systematically disclosed by the Zcash developer team in the latest episode of the Bankless podcast.

Scalability remains the dream come true for privacy public chains. Fortunately, for the Zcash community, its core developers have developed a systematic plan to scale up private ZEC payments. Even more exciting is that the first upgrade toward this goal officially goes live this week.

In the latest Bankless podcast episode, "The Complete Zcash Roadmap," Zcash co-founder Sean Bowe and core protocol contributor Dev Ojha engaged in an in-depth discussion with host David Hoffman. They detailed how to gradually push Zcash's current throughput of approximately 60 KB/s step by step toward Ojha's long-term goal: 50,000 transactions per second (i.e., 100 MB/s throughput, achieving a staggering 166,500% expansion leap).

This article will quickly guide you through the core framework of this vision, outlining the five foundational upgrades supporting this roadmap.

Figure: Zcash Long-Term Network Performance and Throughput Scaling Ladder

Faster Block Times

As I noted when the NU7 timeline was finalized in September, Zcash's ninth major network upgrade will compress the block time from 75 seconds down to 25 seconds. The activation block height for NU7 is expected to be officially reached over the night of November 5-6 UTC.

According to Ojha, assuming the block size remains unchanged, this shift will directly increase the chain's bandwidth by approximately 3x, reaching roughly 180 KB/s. Building on this, he points out that other blockchain-ready techniques can be adopted, such as erasure coding (splitting blocks into redundant data chunks so nodes can reconstruct blocks without downloading all data) and more efficient inter-node Gossip communication protocols.

Notably, while pushing all of this forward, Zcash remains committed to the Proof of Work (PoW) mechanism. Ojha praised this effort as "the first time ever creating a high-throughput Proof of Work network."

However, one objective characteristic must be considered: mining inherently possesses randomness. Therefore, at an average block time of 25 seconds, roughly 1% of blocks will be produced extremely fast within about 250 milliseconds, while another ~1% will take longer than 110 seconds to generate.

Upgrade Status: The faster block speed is scheduled to go live officially this week with the NU7 upgrade. Meanwhile, the more challenging work on breakthrough throughput has been defined by Ojha as a core mission "within the next two years."

PIR Privacy-Retrieval Wallets

As Ojha stated: "The really tricky problem is, how do you know you received money?"

Under Zcash's shielded address system, no external observer can learn who transferred funds to whom. This also means your wallet cannot directly query its own balance from a server like an Ethereum wallet can.

Historically, Zcash wallets had to download every single transaction on-chain and individually compare them locally to determine which ones belonged to them. Once blockchain throughput pushes to 100 MB/s, this raw model requiring every endpoint to download full transaction volumes will inevitably collapse entirely.

This is where Private Information Retrieval (PIR) shines. Under this new paradigm, your terminal wallet sends an encrypted query request to the server storing the on-chain data; leveraging homomorphic encryption (which performs mathematical operations directly on ciphertext data), the server can accurately return the query results without knowing exactly what you queried.

Interestingly, the current flourishing AI wave happens to be the key catalyst for making this privacy technology practical. Ojha explains that this specific type of PIR ultimately boils down to ultra-large-scale matrix-vector multiplication, which precisely happens to be the mathematical domain where GPUs have become extremely cheap and fast due to the AI compute arms race.

To be fair, host David also raised a reasonable question in the conversation: querying a server sounds like introducing a trusted third-party intermediary. In response, Ojha clarified that PIR's operating mechanism will be identical to RPC nodes in the Ethereum ecosystem. Anyone can freely build their own service nodes, and wallet clients can seamlessly switch between numerous different providers.

Upgrade Status: Now in practical application. Bowe revealed that Zcash has already adopted PIR technology in a recent holder on-chain governance vote, which he believes marks a historic first for the crypto industry.

Tachyon Proof Aggregation

Tachyon is a cryptography-layer refactoring project personally led by Bowe, specifically designed to tackle the system's two core bottlenecks. The primary bottleneck is proof computation, because under the current architecture, full nodes must verify the zero-knowledge proof for every shielded transaction individually.

To overcome this hurdle, Tachyon is developing recursive zero-knowledge proofs (Recursive SNARKs, meaning using one proof to verify others), thereby packaging and aggregating massive numbers of proofs. This technology will significantly flatten the verification burden on full nodes, allowing them to verify a single aggregated ZKP here or there, rather than sequentially verifying thousands of independent proofs.

Highly noteworthy is that once deployed and online, the system will immediately deliver at least a 5x performance boost in scalability. If this logic sounds quite familiar, it's because it indeed has precedents. David compared Tachyon's proof aggregation work to the ZK Rollup transaction packing mechanism on Ethereum, to which Ojha frankly acknowledged Ethereum's pioneering contribution in being the first to implement recursive proofs in production environments.

Upgrade Status: Actively under development. Tachyon's code is being integrated into the underlying cryptography protocol stack behind Zakura full nodes, but it has not yet been activated on the mainnet, and the official public release schedule has not been announced.

Stateless Blockchain

The second focus area of the Tachyon project targets solving the State Bloat problem. Every time a user spends shielded ZEC, the network records a Nullifier (the unique tag preventing double-spending of the same funds). Unlike transparent ledgers that can periodically clean up historically accumulated data, privacy blockchains must permanently preserve this continuously expanding nullifier list.

Tachyon is also working on extremal compression of this massive state. According to Ojha, full nodes will eventually only need to retain roughly the active real-time state of the last month, while older historical data will transform into structures that users can trustlessly retrieve if needed. Bowe attributes this innovative technology to an academic paper co-authored with cryptographer Ian Miers.

To be clear, Ojha bluntly states, "You simply cannot cram an extreme 50,000 TPS into a Raspberry Pi," but under this level of extreme compression, running a full node would only require a few hundred gigabytes of storage space, never evolving into a tens-to-hundreds-of-petabytes storage disaster.

Upgrade Status: Currently under active development as a core module of the Tachyon project.

Private RPC Subscription Model

The final upgrade primarily involves economic mechanism design and is also the most conceptualized component among the aforementioned technical roadmap.

In the Ethereum or Solana ecosystems, wallet developers like MetaMask and Phantom fund the operation of RPC servers (the underlying infrastructure responsible for feeding on-chain data to user wallets), partly because they can monetize through user traffic. However, Zcash never tracks its users, so it currently relies solely on a handful of volunteer service providers offering free data support.

To prevent the system from becoming unsustainable long-term by "relying on altruism," Ojha conceptualized a private subscription payment model. Users can pay a fee upfront to purchase, for example, 1,000 queries per month; the wallet converts this quota into a one-time credential token, after which each query consumes one token, built upon the same cryptographic mechanism Zcash uses to prevent double-spending payments.

Therefore, under this paradigm, RPC service providers can accurately verify whether a user holds a valid subscription credential, while remaining completely unaware of exactly which specific subscriber initiated the query.

Upgrade Status: Still in the conceptual design phase, though Ojha emphasizes it is a well-defined engineering problem that is fully solvable.

The Path Forward

As for why all of this appears particularly urgent and important at the current juncture, Bowe's core argument lies in: the explosive popularization of AI tools has reduced the threshold for tracking and pinpointing specific individuals across transparent public chain ledgers to an extremely low, near-zero-cost level.

Beyond the aforementioned thrilling technical blueprint, this roadmap podcast episode deeply explored Zcash's long-term anti-quantum computing planning, formal verification, and on-chain governance architecture. The governance section, in particular, complements and echoes my recent in-depth analysis of the debate over the existence and cancellation of the Zcash developer fund.