diff --git a/services/identity/src/database.rs b/services/identity/src/database.rs
--- a/services/identity/src/database.rs
+++ b/services/identity/src/database.rs
@@ -1,5 +1,7 @@
+use std::collections::HashMap;
+
 use rusoto_core::Region;
-use rusoto_dynamodb::DynamoDbClient;
+use rusoto_dynamodb::{AttributeValue, DynamoDbClient};
 
 pub struct DatabaseClient {
   client: DynamoDbClient,
@@ -12,3 +14,91 @@
     }
   }
 }
+
+type AttributeName = String;
+
+fn construct_primary_key_from_strings(
+  partition_key: (AttributeName, String),
+  sort_key: Option<(AttributeName, String)>,
+) -> HashMap<AttributeName, AttributeValue> {
+  let mut primary_key = HashMap::from([(
+    partition_key.0,
+    AttributeValue {
+      s: Some(partition_key.1),
+      ..Default::default()
+    },
+  )]);
+
+  match sort_key {
+    None => primary_key,
+    Some((name, value)) => {
+      primary_key.insert(
+        name,
+        AttributeValue {
+          s: Some(value),
+          ..Default::default()
+        },
+      );
+      primary_key
+    }
+  }
+}
+
+#[cfg(test)]
+mod tests {
+  use super::*;
+
+  #[test]
+  fn test_construct_primary_key_from_strings_simple() {
+    let partition_key_name = "userID".to_string();
+    let partition_key_value = "12345".to_string();
+    let partition_key =
+      (partition_key_name.clone(), partition_key_value.clone());
+    let primary_key = construct_primary_key_from_strings(partition_key, None);
+    assert_eq!(primary_key.len(), 1);
+    let attribute = primary_key.get(&partition_key_name);
+    assert!(attribute.is_some());
+    assert_eq!(
+      attribute,
+      Some(AttributeValue {
+        s: Some(partition_key_value),
+        ..Default::default()
+      })
+      .as_ref()
+    );
+  }
+
+  #[test]
+  fn test_construct_primary_key_from_strings_composite() {
+    let partition_key_name = "userID".to_string();
+    let partition_key_value = "12345".to_string();
+    let partition_key =
+      (partition_key_name.clone(), partition_key_value.clone());
+    let sort_key_name = "deviceID".to_string();
+    let sort_key_value = "54321".to_string();
+    let sort_key = (sort_key_name.clone(), sort_key_value.clone());
+    let primary_key =
+      construct_primary_key_from_strings(partition_key, Some(sort_key));
+    assert_eq!(primary_key.len(), 2);
+    let partition_key_attribute = primary_key.get(&partition_key_name);
+    assert!(partition_key_attribute.is_some());
+    assert_eq!(
+      partition_key_attribute,
+      Some(AttributeValue {
+        s: Some(partition_key_value),
+        ..Default::default()
+      })
+      .as_ref()
+    );
+    let sort_key_attribute = primary_key.get(&sort_key_name);
+    assert!(sort_key_attribute.is_some());
+    assert_eq!(
+      sort_key_attribute,
+      Some(AttributeValue {
+        s: Some(sort_key_value),
+        ..Default::default()
+      })
+      .as_ref()
+    )
+  }
+}