diff --git a/src/repositories/InMemoryParkingRepository.ts b/src/repositories/InMemoryParkingRepository.ts
index 96488b8..f5c63df 100644
--- a/src/repositories/InMemoryParkingRepository.ts
+++ b/src/repositories/InMemoryParkingRepository.ts
@@ -4,8 +4,9 @@ import {
   IParkingStructureTimestampRecord
 } from "../entities/ParkingRepositoryEntities";
 import { HistoricalParkingAverageQueryResult } from "./ParkingGetterRepository";
+import { CircularQueue } from "../types/CircularQueue";
 
-type ParkingStructureID = string;
+export type ParkingStructureID = string;
 
 // Every 10 minutes
 // 6x per hour * 24x per day * 7x per week = 1008 entries for one week
@@ -19,7 +20,7 @@ export class InMemoryParkingRepository implements ParkingGetterSetterRepository
 
   constructor(
     private structures: Map<ParkingStructureID, IParkingStructure> = new Map(),
-    private historicalData: Map<ParkingStructureID, IParkingStructureTimestampRecord[]> = new Map(),
+    private historicalData: Map<ParkingStructureID, CircularQueue<IParkingStructureTimestampRecord>> = new Map(),
   ) {
   }
 
@@ -44,10 +45,11 @@ export class InMemoryParkingRepository implements ParkingGetterSetterRepository
       };
 
       if (!this.historicalData.has(structure.id)) {
-        this.historicalData.set(structure.id, []);
+        this.historicalData.set(structure.id, new CircularQueue<IParkingStructureTimestampRecord>(MAX_NUM_ENTRIES));
       }
 
-      this.historicalData.get(structure.id)?.push(timestampRecord);
+      const sortingCallback = (a: IParkingStructureTimestampRecord, b: IParkingStructureTimestampRecord) => a.timestampMs - b.timestampMs;
+      this.historicalData.get(structure.id)?.appendWithSorting(timestampRecord, sortingCallback);
       this.dataLastAdded.set(structure.id, new Date(now));
     }
   }
diff --git a/test/repositories/InMemoryParkingRepositoryTests.test.ts b/test/repositories/InMemoryParkingRepositoryTests.test.ts
index b3de36d..24c292f 100644
--- a/test/repositories/InMemoryParkingRepositoryTests.test.ts
+++ b/test/repositories/InMemoryParkingRepositoryTests.test.ts
@@ -1,9 +1,10 @@
 import { beforeEach, describe, expect, it, jest } from "@jest/globals";
 import {
   InMemoryParkingRepository,
-  PARKING_LOGGING_INTERVAL_MS
+  PARKING_LOGGING_INTERVAL_MS, ParkingStructureID
 } from "../../src/repositories/InMemoryParkingRepository";
-import { IParkingStructure } from "../../src/entities/ParkingRepositoryEntities";
+import { IParkingStructure, IParkingStructureTimestampRecord } from "../../src/entities/ParkingRepositoryEntities";
+import { CircularQueue } from "../../src/types/CircularQueue";
 
 describe("InMemoryParkingRepository", () => {
   let repository: InMemoryParkingRepository;
@@ -19,7 +20,7 @@ describe("InMemoryParkingRepository", () => {
     address: "300 E Walnut Ave, Orange, CA 92867",
     updatedTime: new Date(),
   };
-  let historicalData = new Map();
+  let historicalData: Map<ParkingStructureID, CircularQueue<IParkingStructureTimestampRecord>> = new Map();
 
   beforeEach(() => {
     historicalData = new Map();
@@ -57,8 +58,8 @@ describe("InMemoryParkingRepository", () => {
       jest.setSystemTime(now + PARKING_LOGGING_INTERVAL_MS + 60);
       await repository.addOrUpdateParkingStructure(testStructure);
 
-      expect(historicalData.get(testStructure.id)).toContainEqual(expectedTimestampRecordMatcher);
-      expect(historicalData.get(testStructure.id)).toContainEqual({
+      expect(historicalData.get(testStructure.id)?.get(0)).toEqual(expectedTimestampRecordMatcher);
+      expect(historicalData.get(testStructure.id)?.get(1)).toEqual({
         ...expectedTimestampRecordMatcher,
         timestampMs: now + PARKING_LOGGING_INTERVAL_MS + 60,
       });
@@ -74,7 +75,7 @@ describe("InMemoryParkingRepository", () => {
       jest.setSystemTime(now + 60);
       await repository.addOrUpdateParkingStructure(testStructure);
 
-      expect(historicalData.get(testStructure.id)).toHaveLength(1);
+      expect(historicalData.get(testStructure.id)?.size()).toEqual(1);
     });
   });