The blockchain trilemma: the dilemma that hinders global adoption

A blockchain is powerful, but there is a fundamental problem: it cannot be perfect in every way. While many believe that decentralized networks can replace traditional systems, the blockchain trilemma represents the biggest obstacle to overcome. Security, decentralization, and scalability: choosing two means sacrificing the third.

The heart of the problem: why the trilemma exists

Imagine having to choose between three fundamental qualities of a network. Bitcoin can offer security and decentralization, but it processes only about 5 transactions per second. Ethereum reaches 18 TPS, still far from the thousands of transactions handled by Visa. This is not a flaw of poor design, but a structural consequence of decentralization itself.

When multiple independent nodes need to reach a consensus on each transaction, the process becomes slower. Reducing the number of validators would speed up the system, but it would create central points of control, undermining what makes blockchain valuable in the first place.

The concept was popularized by Vitalik Buterin, co-founder of Ethereum, to precisely describe this trade-off: every improvement in one property tends to worsen the other two.

The three pillars of blockchain

Decentralization: who controls the network?

Unlike traditional banks that control the ledgers, a decentralized blockchain distributes data among thousands of participants. No single entity commands. This means that anyone can verify transactions, and the system does not rely on third parties.

But there is a cost: the verification process is slow. The more participants involved, the slower the consensus.

Security: how resistant is it to attacks?

Blockchain security rests on two pillars: encryption and robust consensus mechanisms. Bitcoin uses Proof of Work (PoW), where miners solve complex mathematical puzzles to validate blocks. This makes attacks costly and difficult.

However, security through PoW is computationally intensive, which makes it slow. A network with few nodes is faster, but more vulnerable—a attacker controlling 51% of the power could execute a 51% attack, allowing double spending and other forms of manipulation.

Scalability: how many transactions can it process?

A sustainable blockchain must handle billions of users with fast and inexpensive transactions. Currently, public blockchains reach dozens of TPS while centralized systems exceed a thousand. The reason is simple: centralized environments do not require global consensus.

Increasing scalability by reducing validators, however, compromises security and decentralization, bringing us back to the trilemma.

How the industry is innovating

No blockchain has completely “solved” the trilemma, but several strategies are emerging:

Sharding: divide to conquer

Sharding fragments the network into independent partitions (shard), each of which processes transactions in parallel. A main chain coordinates the interactions between shards.

The NEAR protocol implements the Nightshade 2.0 model: by August 2025, the network operates with 8 active shards and achieves transaction finality in approximately 600 milliseconds. This approach maintains decentralization while drastically improving scalability.

Alternative consensus mechanisms

Proof of Stake (PoS) requires validators to lock up their tokens instead of solving complex calculations. It is less energy-intensive and allows more participants to take part, improving decentralization.

BNB Smart Chain uses Proof of Staked Authority (PoSA), a hybrid model where validators stake BNB and achieve block times of about three seconds. Conflux combines PoW with a Directed Acyclic Graph structure (DAG) to balance security and speed.

Layer 2: build on top, not rebuild

Instead of modifying the base level, Layer 2 solutions process transactions off the main chain and then settle the results on it.

Optimistic rollups ( like Arbitrum) assume that transactions are valid unless disputed. ZK-rollups ( like Scroll) use cryptographic proofs to confirm validity without revealing details. Ethereum is increasingly focused on rollups: DeFi, gaming, and NFTs are moving to Layer 2 for speed and reduced costs.

Bitcoin's Lightning Network uses state channels: two parties make off-chain transactions and only record opening and closing on the blockchain. This allows for instant transactions while maintaining final settlement on Bitcoin.

Towards a scalable future

The blockchain trilemma remains a real challenge, but recent developments are encouraging. Ethereum's roadmap on rollups, the emergence of high-performance modular blockchains, and ongoing innovation in consensus mechanisms show concrete pathways.

The goal is clear: to create systems that maintain the security and decentralization of a blockchain while processing transactions like a centralized network. We are not there yet, but the industry is moving in the right direction towards achieving global adoption without significant trade-offs.