Add indexers to architecture diagram (#307)

* Add info about indexers and block explorers

* update diagram and hard-code it

docs/architecture.mdx → docs/architecture.md

@@ -2,11 +2,9 @@
 title: Architecture
 authors: Tim McMackin
 last_update:
-  date: 28 November 2023
+  date: 6 February 2024
 ---
 
-import LucidDiagram from '@site/src/components/LucidDiagram';
-
 The Tezos blockchain is composed of many Tezos nodes running around the world, complemented by other running daemons, such as bakers and accusers.
 These processes collaborate with the overall goal of maintaining the blockchain data in a decentralized manner.
 
@@ -15,7 +13,8 @@ Users interact with nodes through many different clients, including command-line
 
 This diagram shows a high-level view of the Tezos system:
 
-<LucidDiagram width="640px" height="480px" src="https://lucid.app/documents/embedded/d778aa2a-ad0a-4324-b235-ed3b35742c58" id="Uz-K28y3R8gJ" />
+![A high-level view of the Tezos system, including Tezos nodes, the blockchain data itself, an Indexer, and a few examples of clients](/img/architecture/architecture-overview.png)
+<!-- https://lucid.app/lucidchart/d778aa2a-ad0a-4324-b235-ed3b35742c58/edit -->
 
 ## The blockchain data
 
@@ -147,6 +146,11 @@ Some typical use cases for nodes are:
 Optionally, this node can open its RPC interface to serve different kinds of requests.
 - A node along with a baker, an accuser, and a signer can be used to bake new blocks, activity which ensures that the blockchain progresses and yields rewards in tokens.
 
+### Indexers and block explorers
+
+Indexers are off-chain applications that retrieve blockchain data, process it, and store it in a way that makes it easier to search and use.
+They are an important part of block explorers, which are applications that provide data about the blockchain.
+
 ## References
 
 For more information about the architecture of Tezos, see:
@@ -155,3 +159,5 @@ For more information about the architecture of Tezos, see:
 - [Tokens](./architecture/tokens)
 - [Smart Optimistic Rollups](./architecture/smart-rollups)
 - [Governance](./architecture/governance)
+- [Indexers](./developing/information/indexers)
+- [Block explorers](./developing/information/block-explorers)