From 727a2f8bba898010ee72a8d8405b16ef91630489 Mon Sep 17 00:00:00 2001
From: John Richardson <42470533+John-Richardson@users.noreply.github.com>
Date: Tue, 7 Jul 2020 03:05:50 +0200
Subject: [PATCH] Remove redundant SQL index in Pastebin exercise (#405)

---
 solutions/system_design/pastebin/README.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/solutions/system_design/pastebin/README.md b/solutions/system_design/pastebin/README.md
index 756c78c..2d87ddc 100644
--- a/solutions/system_design/pastebin/README.md
+++ b/solutions/system_design/pastebin/README.md
@@ -116,7 +116,7 @@ paste_path varchar(255) NOT NULL
 PRIMARY KEY(shortlink)
 ```
 
-We'll create an [index](https://github.com/donnemartin/system-design-primer#use-good-indices) on `shortlink ` and `created_at` to speed up lookups (log-time instead of scanning the entire table) and to keep the data in memory.  Reading 1 MB sequentially from memory takes about 250 microseconds, while reading from SSD takes 4x and from disk takes 80x longer.<sup><a href=https://github.com/donnemartin/system-design-primer#latency-numbers-every-programmer-should-know>1</a></sup>
+Setting the primary key to be based on the `shortlink` column creates an [index](https://github.com/donnemartin/system-design-primer#use-good-indices) that the database uses to enforce uniqueness. We'll create an additional index on `created_at` to speed up lookups (log-time instead of scanning the entire table) and to keep the data in memory.  Reading 1 MB sequentially from memory takes about 250 microseconds, while reading from SSD takes 4x and from disk takes 80x longer.<sup><a href=https://github.com/donnemartin/system-design-primer#latency-numbers-every-programmer-should-know>1</a></sup>
 
 To generate the unique url, we could: