# Where CEXs Leak Efficiency

*CEXs Are Onchain Execution Engines*

By [Spire Labs](https://paragraph.com/@spire) · 2026-05-06

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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
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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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*Originally published on [Spire Labs](https://paragraph.com/@spire/where-cexs-leak-efficiency)*