# Where CEXs Leak Efficiency

> CEXs Are Onchain Execution Engines

**Published by:** [Spire Labs](https://paragraph.com/@spire/)
**Published on:** 2026-05-06
**URL:** https://paragraph.com/@spire/where-cexs-leak-efficiency

## Content

The moment your backend signs and submits transactions on behalf of users, your business changes. You are no longer just a trading platform or custodian. You are an execution engine. Most CEXs run that engine inefficiently. Once you control signing, execution becomes a cost center, and most teams under-optimize it. Backend-Signed Execution Systems Centralized exchanges fall into a category that doesn’t get enough attention: backend-signed execution systems. These systems: Construct transactions server-side Control calldata and execution structure Pass gas costs to users (often with a buffer) In a CEX, this includes: Withdrawals Deposit sweeping Hot ↔ cold wallet rebalancing Internal settlement Cross-chain liquidity movement There is no external signer. Everything is coordinated internally, signed by your infrastructure (or MPC provider), and executed at your expense. Which means: Execution inefficiency directly impacts both margins and user experience. The Hidden Cost Center Most exchanges optimize for: Volume Liquidity Fees Latency But under the hood, they run a high-throughput execution pipeline. Where inefficiency shows up One withdrawal = one transaction Repeated logic with fixed overhead per user The same contract calls encoded over and over No aggregation or batching across users Identical transfers executed independently Systems built for correctness, not efficiency Why it’s missed At small scale, costs are negligible. At large scale, they compound across millions of transactions. Execution quietly becomes one of the largest unoptimized cost centers in a CEX. Where CEXs Leak Efficiency Withdrawals Pattern: One request → one transaction Opportunity: Batch across users Share execution overhead Deposit Sweeping Pattern: Individual sweeps from deposit addresses Opportunity: Aggregate transfers Reduce repeated contract calls Rebalancing Pattern: Independent transfers across wallets and assets Opportunity: Combine flows Optimize timing and batching Internal Onchain Flows Even mostly offchain systems still: Move funds Reconcile balances Opportunity: Treat internal operations as batchable units Reduce routine execution cost Spire: Execution Optimization as Infrastructure Spire Labs builds DA Builder, a transaction aggregation layer for Ethereum. It sits between your backend and the chain, combining multiple transactions into a single optimized execution. DA Builder: Combines multiple transactions into a single onchain transaction Reduces redundant overhead and execution costs Shares calldata across transactions Lowers gas and calldata costs Improves inclusion via higher-value bundled transactions Adds built-in MEV and revert protection Framed simply: Execution infrastructure for teams that already own transaction flow No changes to: UX Product logic Core systems Just more efficient execution. Why It Matters Margin Expansion Lower gas per action directly improves unit economics. Better User Economics Cheaper execution enables lower fees and better pricing. Non-Linear Scaling Batching reduces cost per transaction as volume grows. The Shift If your backend signs transactions, execution is your responsibility. Most CEXs today: Treat execution as plumbing Accept default patterns Ignore aggregation That won’t hold. Execution optimization will become standard infrastructure, like CDNs in Web2. And exchanges that adopt it early will have a structural advantage: Lower costs Better pricing More scalable systems Because ultimately: If you control signing, you control execution. And execution is worth optimizing.

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