> For the complete documentation index, see [llms.txt](https://docs.secured.finance/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.secured.finance/fixed-rate-lending/advanced-topics/orderbook-deep-dive.md).

# Orderbook Deep Dive

A full on-chain order book is widely considered impractical: every open order is state, and Solidity storage writes are expensive. Three operations in particular scale badly with data volume — creating open orders, executing market orders against many resting orders, and rolling every position at maturity. Naively implemented, these can approach the block gas limit.

**Secured Finance runs a full on-chain order book anyway**, using three complementary techniques:

| Technique                                                                                                                           | What it solves                                                                                                                             |
| ----------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------ |
| [**Red-Black Tree**](/fixed-rate-lending/advanced-topics/orderbook-deep-dive/red-black-tree.md)                                     | O(log n) insertion, deletion, and best-price lookup for orders, with a custom *unlink* operation for bulk removal of matched orders        |
| [**Lazy Evaluation**](/fixed-rate-lending/advanced-topics/orderbook-deep-dive/lazy-evaluation.md)                                   | Defers state updates until a user actually acts — filled orders and matured positions are recomputed on read, not rewritten on every event |
| [**Genesis Value & Compound Factor**](/fixed-rate-lending/advanced-topics/orderbook-deep-dive/genesis-value-and-compound-factor.md) | Rolls *every* position at maturity by updating a single factor, instead of touching each position individually                             |

Supporting structure: [**Orderbook Rotation**](/fixed-rate-lending/advanced-topics/orderbook-deep-dive/orderbook-rotation.md) caps each currency at 9 order books (8 active + 1 pre-open), recycling matured markets so the data subject to lazy evaluation stays bounded.

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**Why bother?** Liquidity pools are simpler, but pool rates lack the transparency, composability, and term structure of an order book. Fixed income needs real price discovery at each maturity — that's what this architecture buys.
{% endhint %}