Crosschain infrastructure demand breaks public testnet — 2 key lessons for builders

The promise of Bitcoin (BTC) has always been immense: a decentralized, trustless system capable of transforming the global financial landscape. However, as its popularity grows, so do its challenges. While the core layer remains robust, Bitcoin needs better scalability to meet the demands of a growing user base and pave the way for innovative advancements in blockchain technology.

Scalability becomes an even greater challenge during testnets — simulated ecosystems designed to mimic real-world usage. Public testnets, designed to benefit developers despite their inherent limitations, often buckle under the weight of high demand and expose weaknesses in the broader blockchain infrastructure.

A recent event has underscored this scalability issue. The testnet launch of Portal to Bitcoin, a bridgeless crosschain infrastructure, began as a controlled experiment but quickly turned into an unplanned stress test.

Initially designed to handle a few thousand testers, the rollout attracted over 100,000 users in just 36 hours. While this overwhelming response demonstrated the platform’s appeal, it also exposed critical bottlenecks in the existing blockchain testnet infrastructure, including:

• The scalability limitations of current Bitcoin testnets
• The inherent challenges posed by Lightning Network constraints

Through swift and innovative action, the team effectively addressed these challenges, offering valuable insights and guidance for blockchain developers navigating similar obstacles.

Bitcoin faces real-world constraints

Portal enables effortless, non-custodial and crosschain swaps between Bitcoin, Ethereum and eventually other blockchains like Solana. It allows users to interact with multiple blockchains simultaneously without the need for traditional crypto wallets, aiming to simplify the complexities of decentralized trading. The testnet launch was intended to showcase all these functionalities in a controlled environment.

However, the influx of users revealed significant limitations not caused by Portal’s shortcomings but by the constraints of its surrounding testnet ecosystem. Existing Bitcoin and Ethereum testnets, designed for limited developer testing, were overwhelmed under the weight of unprecedented demand. Transactions ground to a halt, faucet services dried up and the infrastructure supporting Bitcoin Lightning Network channels collapsed under the pressure of hundreds of thousands of new nodes.

With 102,000 nodes and 120,000 channels, Portal surpassed the testnet’s capacity of 54,000 nodes and 42,000 channels.

All these hurdles shone a spotlight on one undeniable truth: The very constraints meant to help developers test their concepts were simply not built for the overwhelming interest Portal saw.

Turning trials into triumphs

Technical bottlenecks forced the Portal’s team to address issues outside the boundaries of their technology.

The team was well aware of the chronic issues plaguing current Bitcoin testnets, including slow block confirmation times and limited scalability. To address these challenges, they initially relied on a Lightning Service Provider (LSP), which offered users a paid Lightning channel.

However, as transaction confirmation times ballooned to three days under high demand, the team shifted to Mutinynet, a custom testnet designed to offer better networking capabilities. Yet, the overwhelming user demand ultimately caused Mutinynet to crash as well.

The average gas cost increased as soon as Portal opened its testnet to Discord members.

Ultimately, the team faced a pivotal challenge: overcoming the obstacles posed by the surrounding testnet environments. Finding silver linings in this challenge and turning it into a catalyst for innovation, they implemented a series of strategic changes:

• Forking infrastructure: The team forked Mutinynet, gaining full control over the infrastructure and surmounting the limitations of public testnets.
• Faucet management: Portal replaced centralized faucets, which were the target of bot attacks, with onchain token distribution to enhance reliability and security.
• Dynamic fees: When high demand spiked gas fees on Ethereum’s testnet and caused transaction failures, the team responded by developing a dynamic fee mechanism.

In addition to strategic changes, the engineering team quickly developed exchange protocols, browser extensions and mobile applications to ensure the platform could adapt to changing challenges. With these rapid interventions, the portal team stabilized the testnet and maintained user engagement.

Lessons for the blockchain ecosystem

Despite the challenges, the testnet provided invaluable insights into the complexities of crosschain interoperability and the paramount importance of user experience.

The community’s support was a key driver of this progress. Users were instrumental in identifying bugs, suggesting features and validating improvements. In addition to simply participating, many community members stepped forward to help distribute tokens, reflecting a deep commitment to the project’s growth.

The Aurelia Testnet launch has been nothing short of a success!

In just 36 hours, what we planned as a controlled rollout for a few thousand testers exploded into 150,000+ users eager to experience custodyless, cross-chain swaps.

Here’s the story so far. 🧵 pic.twitter.com/4vhTV2jg4j

— Portal (@PortaltoBitcoin) December 13, 2024

In response to user feedback, Portal introduced a seven-day cohort program in which select groups of users were given full access to testnet swaps on specific days. The program addressed congestion issues while maintaining a balanced testing environment. Even on “off” days, users could continue to interact, explore features and manage wallets without overwhelming the system.

This community-centric approach solved immediate scalability concerns and also laid the groundwork for a more resilient and scalable mainnet launch.

Road to the mainnet

By the end of the challenging testnet phase, Portal showcased its capability to execute fast, non-custodial swaps between major blockchains. The team also made strides in enhancing transaction processing times through innovative optimizations and established a robust, feedback-driven development pipeline to facilitate continuous improvement.

Strengthened by the invaluable lessons learned during the intensive testing period, the team is focused on expanding blockchain support, improving the platform’s user interface and conducting comprehensive security audits. The testnet experience has turned the crisis into an opportunity to learn and grow, and Portal is working toward a smooth transition to the mainnet.

The lessons learned during this ambitious testnet phase extend far beyond a single project, highlighting the broader challenges and possibilities within the blockchain ecosystem. As decentralized technologies evolve, they must address the demands of today while anticipating tomorrow’s exponential growth.