1 files changed, 122 insertions, 8 deletions
diff --git a/_slides/2020-10-22-datomic-on-global-good-reasons-for-and-against-it.slides b/_slides/2020-10-22-datomic-on-global-good-reasons-for-and-against-it.slides
index a18700d..8f207c9 100644
--- a/_slides/2020-10-22-datomic-on-global-good-reasons-for-and-against-it.slides
+++ b/_slides/2020-10-22-datomic-on-global-good-reasons-for-and-against-it.slides
@@ -13,16 +13,23 @@ published: false
 
 ---
 
+# Premise
+
+Datomic's bottleneck is **write** throughput, not read
+
+---
+
 When creating a new service...
 
 ---
 
 ```clojure
-(defn prototype->database
-  [prototype]
-  (if (= :global prototype)
-    :datomic
-    #{:dynamodb :redis :nothing}))
+(defn database-for-service
+  [service]
+  (let [prototype (prototype-for-service service)]
+    (if (= :global prototype)
+      :datomic
+      #{:dynamodb :redis :nothing})))
 ```
 
 ---
@@ -31,11 +38,117 @@ When creating a new service...
 
 ---
 
-notifications vs toasty
+The deciding factor shouldn't be the prototype, but the **cardinality**
+
+---
+
+```diff
+ (defn database-for-service
+   [service]
+-  (let [prototype (prototype-for-service service)]
+-    (if (= :global prototype)
+-      :datomic
+-      #{:dynamodb :redis :nothing})))
++  (let [cardinality (cardinality-for-service service)]
++    (if (= :too-high cardinality)
++      #{:dynamodb :redis :nothing
++      :datomic))))
+```
+
+---
+
+```clojue
+(defn database-for-service
+  [service]
+  (let [cardinality (cardinality-for-service service)]
+    (if (= :too-high cardinality)
+      #{:dynamodb :redis :nothing
+      :datomic))))
+```
+
+---
+
+But how to determine when the cardinality is
+
+**`:too-high`**?
+
+---
+
+Let's think about the cardinality of existing services we know
+
+---
+
+What is the cardinality of...
+
+---
+
+# savings-accounts
+
+---
+
+# inductor
+
+---
+
+# crebito
+
+---
+
+# diablo
+
+---
+
+# lost-boy?
+
+---
+
+# hook?
+
+---
+
+# ledger
+
+---
+
+# blackleach
+
+---
+
+# notification
+
+---
+
+# toasty
+
+---
+
+# auth
+
+---
+
+# waypoint
+
+---
+
+# jurassic-park
+
+---
+
+Compare the database choice of services with similar cardinalities:
+
+## notifications vs toasty
+
+---
+
+Compare different cardinalities for services on global prototype:
+
+## jurassic-park vs auth
+
+---
 
-jurassic-park vs auth
+Compare different cardinality for different services inside the same domain:
 
-blackleach -> diablo -> ledger
+## savings-accounts -> blackleach -> diablo -> ledger
 
 ---
 
@@ -45,3 +158,4 @@ References:
 
 1. these slides: [{{ site.tld }}/slides.html]({% link slides.md %})
 2. [prose version of this presentation]({% link _articles/2020-10-22-datomic-on-global-good-reasons-for-and-against-it.md %})
+3. "[Understanding Database Sharding](https://www.digitalocean.com/community/tutorials/understanding-database-sharding)"