diff --git a/src/matrix/storage/memory/stores/RoomTimelineStore.js b/src/matrix/storage/memory/stores/RoomTimelineStore.js
new file mode 100644
index 00000000..a5072dba
--- /dev/null
+++ b/src/matrix/storage/memory/stores/RoomTimelineStore.js
@@ -0,0 +1,220 @@
+import SortKey from "../sortkey.js";
+import sortedIndex from "../../../utils/sortedIndex.js";
+
+function compareKeys(key, entry) {
+    if (key.roomId === entry.roomId) {
+        return key.sortKey.compare(entry.sortKey);
+    } else {
+        return key.roomId < entry.roomId ? -1 : 1;
+    }
+}
+
+class Range {
+    constructor(timeline, lower, upper, lowerOpen, upperOpen) {
+        this._timeline = timeline;
+        this._lower = lower;
+        this._upper = upper;
+        this._lowerOpen = lowerOpen;
+        this._upperOpen = upperOpen;
+    }
+
+    /** projects the range onto the timeline array */
+    project(roomId, maxCount = Number.MAX_SAFE_INTEGER) {
+        // determine lowest and highest allowed index.
+        // Important not to bleed into other roomIds here.
+        const lowerKey = {roomId, sortKey: this._lower || SortKey.minKey };
+        // apply lower key being open (excludes given key)
+        let minIndex = sortedIndex(this._timeline, lowerKey, compareKeys);
+        if (this._lowerOpen && minIndex < this._timeline.length && compareKeys(lowerKey, this._timeline[minIndex]) === 0) {
+            minIndex += 1;
+        }
+        const upperKey = {roomId, sortKey: this._upper || SortKey.maxKey };
+        // apply upper key being open (excludes given key)
+        let maxIndex = sortedIndex(this._timeline, upperKey, compareKeys);
+        if (this._upperOpen && maxIndex < this._timeline.length && compareKeys(upperKey, this._timeline[maxIndex]) === 0) {
+            maxIndex -= 1;
+        }
+        // find out from which edge we should grow
+        // if upper or lower bound
+        // again, important not to go below minIndex or above maxIndex
+        // to avoid bleeding into other rooms
+        let startIndex, endIndex;
+        if (!this._lower && this._upper) {
+            startIndex = Math.max(minIndex, maxIndex - maxCount);
+            endIndex = maxIndex;
+        } else if (this._lower && !this._upper) {
+            startIndex = minIndex;
+            endIndex = Math.min(maxIndex, minIndex + maxCount);
+        } else {
+            startIndex = minIndex;
+            endIndex = maxIndex;
+        }
+        
+        // if startIndex is out of range, make range empty
+        if (startIndex === this._timeline.length) {
+            startIndex = endIndex = 0;
+        }
+        const count = endIndex - startIndex;
+        return {startIndex, count};
+    }
+
+    select(roomId, maxCount) {
+        const {startIndex, count} = this.project(roomId, this._timeline, maxCount);
+        return this._timeline.slice(startIndex, startIndex + count);
+    }
+}
+
+export default class RoomTimelineStore {
+    constructor(initialTimeline = []) {
+        this._timeline = initialTimeline;
+    }
+
+    /** Creates a range that only includes the given key
+     *  @param {SortKey} sortKey the key
+     *  @return {Range} the created range
+     */
+    onlyRange(sortKey) {
+        return new Range(this._timeline, sortKey, sortKey);
+    }
+
+    /** Creates a range that includes all keys before sortKey, and optionally also the key itself.
+     *  @param {SortKey} sortKey the key
+     *  @param {boolean} [open=false] whether the key is included (false) or excluded (true) from the range at the upper end.
+     *  @return {Range} the created range
+     */
+    upperBoundRange(sortKey, open=false) {
+        return new Range(this._timeline, undefined, sortKey, undefined, open);
+    }
+
+    /** Creates a range that includes all keys after sortKey, and optionally also the key itself.
+     *  @param {SortKey} sortKey the key
+     *  @param {boolean} [open=false] whether the key is included (false) or excluded (true) from the range at the lower end.
+     *  @return {Range} the created range
+     */
+    lowerBoundRange(sortKey, open=false) {
+        return new Range(this._timeline, sortKey, undefined, open);
+    }
+
+    /** Creates a range that includes all keys between `lower` and `upper`, and optionally the given keys as well.
+     *  @param {SortKey} lower the lower key
+     *  @param {SortKey} upper the upper key
+     *  @param {boolean} [lowerOpen=false] whether the lower key is included (false) or excluded (true) from the range.
+     *  @param {boolean} [upperOpen=false] whether the upper key is included (false) or excluded (true) from the range.
+     *  @return {Range} the created range
+     */
+    boundRange(lower, upper, lowerOpen=false, upperOpen=false) {
+        return new Range(this._timeline, lower, upper, lowerOpen, upperOpen);
+    }
+
+    /** Looks up the last `amount` entries in the timeline for `roomId`.
+     *  @param  {string} roomId
+     *  @param  {number} amount
+     *  @return {Promise<Entry[]>} a promise resolving to an array with 0 or more entries, in ascending order.
+     */
+    lastEvents(roomId, amount) {
+        return this.eventsBefore(roomId, SortKey.maxKey, amount);
+    }
+
+    /** Looks up the first `amount` entries in the timeline for `roomId`.
+     *  @param  {string} roomId
+     *  @param  {number} amount
+     *  @return {Promise<Entry[]>} a promise resolving to an array with 0 or more entries, in ascending order.
+     */
+    firstEvents(roomId, amount) {
+        return this.eventsAfter(roomId, SortKey.minKey, amount);
+    }
+
+    /** Looks up `amount` entries after `sortKey` in the timeline for `roomId`.
+     *  The entry for `sortKey` is not included.
+     *  @param  {string} roomId
+     *  @param  {SortKey} sortKey
+     *  @param  {number} amount
+     *  @return {Promise<Entry[]>} a promise resolving to an array with 0 or more entries, in ascending order.
+     */
+    eventsAfter(roomId, sortKey, amount) {
+        const events = this.lowerBoundRange(sortKey, true).select(roomId, amount);
+        return Promise.resolve(events);
+    }
+
+    /** Looks up `amount` entries before `sortKey` in the timeline for `roomId`.
+     *  The entry for `sortKey` is not included.
+     *  @param  {string} roomId
+     *  @param  {SortKey} sortKey
+     *  @param  {number} amount
+     *  @return {Promise<Entry[]>} a promise resolving to an array with 0 or more entries, in ascending order.
+     */
+    eventsBefore(roomId, sortKey, amount) {
+        const events = this.upperBoundRange(sortKey, true).select(roomId, amount);
+        return Promise.resolve(events);
+    }
+
+    /** Looks up the first, if any, event entry (so excluding gap entries) after `sortKey`.
+     *  @param  {string} roomId
+     *  @param  {SortKey} sortKey
+     *  @return {Promise<(?Entry)>} a promise resolving to entry, if any.
+     */
+    nextEvent(roomId, sortKey) {
+        const searchSpace = this.lowerBoundRange(sortKey, true).select(roomId);
+        const event = searchSpace.find(entry => !!entry.event);
+        return Promise.resolve(event);
+    }
+
+    /** Looks up the first, if any, event entry (so excluding gap entries) before `sortKey`.
+     *  @param  {string} roomId
+     *  @param  {SortKey} sortKey
+     *  @return {Promise<(?Entry)>} a promise resolving to entry, if any.
+     */
+    previousEvent(roomId, sortKey) {
+        const searchSpace = this.upperBoundRange(sortKey, true).select(roomId);
+        const event = searchSpace.reverse().find(entry => !!entry.event);
+        return Promise.resolve(event);
+    }
+
+    /** Inserts a new entry into the store. The combination of roomId and sortKey should not exist yet, or an error is thrown.
+     *  @param  {Entry} entry the entry to insert
+     *  @return {Promise<>} a promise resolving to undefined if the operation was successful, or a StorageError if not.
+     *  @throws {StorageError} ...
+     */
+    insert(entry) {
+        const insertIndex = sortedIndex(this._timeline, entry, compareKeys);
+        if (insertIndex < this._timeline.length) {
+            const existingEntry = this._timeline[insertIndex];
+            if (compareKeys(entry, existingEntry) === 0) {
+                return Promise.reject(new Error("entry already exists"));
+            }
+        }
+        this._timeline.splice(insertIndex, 0, entry);
+        return Promise.resolve();
+    }
+
+    /** Updates the entry into the store with the given [roomId, sortKey] combination.
+     *  If not yet present, will insert. Might be slower than add.
+     *  @param  {Entry} entry the entry to update.
+     *  @return {Promise<>} a promise resolving to undefined if the operation was successful, or a StorageError if not.
+     */
+    update(entry) {
+        let update = false;
+        const updateIndex = sortedIndex(this._timeline, entry, compareKeys);
+        if (updateIndex < this._timeline.length) {
+            const existingEntry = this._timeline[updateIndex];
+            if (compareKeys(entry, existingEntry) === 0) {
+                update = true;
+            }
+        }
+        this._timeline.splice(updateIndex, update ? 1 : 0, entry);
+        return Promise.resolve();
+    }
+
+    get(roomId, sortKey) {
+        const range = this.onlyRange(sortKey);
+        const {startIndex, count} = range.project(roomId);
+        const event = count ? this._timeline[startIndex] : undefined;
+        return Promise.resolve(event);
+    }
+
+    removeRange(roomId, range) {
+        const {startIndex, count} = range.project(roomId);
+        const removedEntries = this._timeline.splice(startIndex, count);
+        return Promise.resolve(removedEntries);
+    }
+}