diff --git a/components/ads-client/src/ads_store.rs b/components/ads-client/src/ads_store.rs
new file mode 100644
index 00000000000..8b52783f1d4
--- /dev/null
+++ b/components/ads-client/src/ads_store.rs
@@ -0,0 +1,270 @@
+use crate::mars::ad_response::{AdImage, AdSpoc, AdTile};
+use std::{
+    collections::HashMap,
+    time::{Duration, Instant},
+};
+
+const DEFAULT_TTL: Duration = Duration::from_secs(300);
+
+// TODO: This is an intentionally naive in-memory cache implementation of the ads cache.
+// It functions as a skeleton to store ads fetched in the background, and has a naive expiration mechanism.
+// The subsequent vertical slice will replace this in its entirety with the http_cache sqlite database instead, with TTLs, persistent storage, etc.
+#[derive(Debug)]
+pub struct AdsStore {
+    ttl: Duration,
+
+    image_ads: HashMap<PlacementId, CacheEntry<AdImage>>,
+    spoc_ads: HashMap<PlacementId, CacheEntry<Vec<AdSpoc>>>,
+    tile_ads: HashMap<PlacementId, CacheEntry<AdTile>>,
+}
+
+/// Identification of placement sent and returned from MARS (eg: `mock_spoc_1`)
+#[derive(Debug, Hash, PartialEq, Eq, Clone)]
+pub struct PlacementId(String);
+
+impl Default for AdsStore {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl AdsStore {
+    pub fn new() -> Self {
+        AdsStore::new_with_ttl(DEFAULT_TTL)
+    }
+
+    pub fn new_with_ttl(ttl: Duration) -> Self {
+        AdsStore {
+            ttl,
+            image_ads: HashMap::new(),
+            spoc_ads: HashMap::new(),
+            tile_ads: HashMap::new(),
+        }
+    }
+
+    pub fn store_ads<T: AdsStorable>(
+        &mut self,
+        ads: HashMap<PlacementId, T::StorageType>,
+        timestamp: Instant,
+    ) {
+        T::store_ads(ads, self, timestamp);
+    }
+
+    pub fn get_stored_ads<'a, T: AdsStorable>(
+        &'a self,
+        placement: &PlacementId,
+    ) -> Option<&'a T::StorageType> {
+        T::fetch_stored_ads(self, placement)
+    }
+}
+
+pub trait AdsStorable: Sized {
+    // The ad(s) to store (eg: this may be a single ad, or an array of ads)
+    type StorageType;
+
+    fn store_ads(
+        ads: HashMap<PlacementId, Self::StorageType>,
+        ads_cache: &mut AdsStore,
+        timestamp: Instant,
+    );
+    fn fetch_stored_ads<'a>(
+        ads_cache: &'a AdsStore,
+        id: &PlacementId,
+    ) -> Option<&'a Self::StorageType>;
+}
+
+impl AdsStorable for AdImage {
+    type StorageType = AdImage;
+    fn store_ads(ads: HashMap<PlacementId, AdImage>, ads_cache: &mut AdsStore, timestamp: Instant) {
+        ads_cache.image_ads.extend(
+            ads.into_iter()
+                .map(|(key, ad)| (key, CacheEntry::new(ad, timestamp))),
+        );
+        ads_cache
+            .image_ads
+            .retain(|_, x| !x.is_expired(ads_cache.ttl));
+    }
+
+    fn fetch_stored_ads<'a>(ads_cache: &'a AdsStore, id: &PlacementId) -> Option<&'a AdImage> {
+        ads_cache.image_ads.get(id).map(|ads| ads.get_value())
+    }
+}
+
+impl AdsStorable for AdSpoc {
+    type StorageType = Vec<AdSpoc>;
+    fn store_ads(
+        ads: HashMap<PlacementId, Vec<AdSpoc>>,
+        ads_cache: &mut AdsStore,
+        timestamp: Instant,
+    ) {
+        ads_cache.spoc_ads.extend(
+            ads.into_iter()
+                .map(|(key, ad)| (key, CacheEntry::new(ad, timestamp))),
+        );
+        ads_cache
+            .spoc_ads
+            .retain(|_, x| !x.is_expired(ads_cache.ttl));
+    }
+    fn fetch_stored_ads<'a>(ads_cache: &'a AdsStore, id: &PlacementId) -> Option<&'a Vec<AdSpoc>> {
+        ads_cache.spoc_ads.get(id).map(|ads| ads.get_value())
+    }
+}
+
+impl AdsStorable for AdTile {
+    type StorageType = AdTile;
+    fn store_ads(ads: HashMap<PlacementId, AdTile>, ads_cache: &mut AdsStore, timestamp: Instant) {
+        ads_cache.tile_ads.extend(
+            ads.into_iter()
+                .map(|(key, ad)| (key, CacheEntry::new(ad, timestamp))),
+        );
+        ads_cache
+            .tile_ads
+            .retain(|_, x| !x.is_expired(ads_cache.ttl));
+    }
+    fn fetch_stored_ads<'a>(ads_cache: &'a AdsStore, id: &PlacementId) -> Option<&'a AdTile> {
+        ads_cache.tile_ads.get(id).map(|ads| ads.get_value())
+    }
+}
+
+#[derive(Debug)]
+struct CacheEntry<T> {
+    inserted_at: Instant,
+    value: T,
+}
+
+impl<T> CacheEntry<T> {
+    fn new(value: T, instant: Instant) -> CacheEntry<T> {
+        CacheEntry {
+            inserted_at: instant,
+            value,
+        }
+    }
+
+    fn is_expired(&self, ttl: Duration) -> bool {
+        self.inserted_at.elapsed() >= ttl
+    }
+
+    fn get_value(&self) -> &T {
+        &self.value
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::{
+        collections::HashMap,
+        time::{Duration, Instant},
+    };
+
+    use crate::{
+        ads_store::{AdsStore, PlacementId},
+        mars::ad_response::{AdImage, AdSpoc, AdTile},
+        test_utils,
+    };
+
+    #[test]
+    fn test_store_image_ad() {
+        let one_min_ago = Instant::now()
+            .checked_sub(Duration::from_secs(60))
+            .expect("Could not create `Instant` for 5 minutes ago");
+        let five_sec_ago = Instant::now()
+            .checked_sub(Duration::from_secs(5))
+            .expect("Could not create `Instant` for 1 minute ago");
+        let mut ads_store = AdsStore::new_with_ttl(Duration::from_secs(30));
+
+        let demo_ads = test_utils::get_example_happy_image_response().data;
+        let demo_ads: HashMap<PlacementId, AdImage> = demo_ads
+            .clone()
+            .into_iter()
+            .filter_map(|(k, v)| Some((PlacementId(k), v.into_iter().next()?)))
+            .collect();
+        let first_key = demo_ads
+            .iter()
+            .next()
+            .expect("No test data in `get_example_happy_image_response`")
+            .0;
+
+        ads_store.store_ads::<AdImage>(demo_ads.clone(), one_min_ago);
+        assert!(
+            ads_store.get_stored_ads::<AdImage>(first_key).is_none(),
+            "Old data past TTL date must not be returned."
+        );
+
+        ads_store.store_ads::<AdImage>(demo_ads.clone(), five_sec_ago);
+        assert!(
+            ads_store.get_stored_ads::<AdImage>(first_key).is_some(),
+            "Could not fetch fresh ad from ads store."
+        );
+    }
+
+    #[test]
+    fn test_store_spocs_ad() {
+        let one_min_ago = Instant::now()
+            .checked_sub(Duration::from_secs(60))
+            .expect("Could not create `Instant` for 5 minutes ago");
+        let five_sec_ago = Instant::now()
+            .checked_sub(Duration::from_secs(5))
+            .expect("Could not create `Instant` for 1 minute ago");
+        let mut ads_store = AdsStore::new_with_ttl(Duration::from_secs(30));
+
+        let demo_ads = test_utils::get_example_happy_spoc_response().data;
+        let demo_ads: HashMap<PlacementId, Vec<AdSpoc>> = demo_ads
+            .clone()
+            .into_iter()
+            .map(|(k, v)| (PlacementId(k), v))
+            .collect();
+        let first_key = demo_ads
+            .iter()
+            .next()
+            .expect("No test data in `get_example_happy_spoc_response`")
+            .0;
+
+        ads_store.store_ads::<AdSpoc>(demo_ads.clone(), one_min_ago);
+        assert!(
+            ads_store.get_stored_ads::<AdSpoc>(first_key).is_none(),
+            "Old data past TTL date must not be returned."
+        );
+
+        ads_store.store_ads::<AdSpoc>(demo_ads.clone(), five_sec_ago);
+        assert!(
+            ads_store.get_stored_ads::<AdSpoc>(first_key).is_some(),
+            "Could not fetch fresh ad from ads store."
+        );
+    }
+
+    #[test]
+
+    fn test_store_tiles_ad() {
+        let one_min_ago = Instant::now()
+            .checked_sub(Duration::from_secs(60))
+            .expect("Could not create `Instant` for 5 minutes ago");
+        let five_sec_ago = Instant::now()
+            .checked_sub(Duration::from_secs(5))
+            .expect("Could not create `Instant` for 1 minute ago");
+        let mut ads_store = AdsStore::new_with_ttl(Duration::from_secs(30));
+
+        let demo_ads = test_utils::get_example_happy_uatile_response().data;
+        let demo_ads: HashMap<PlacementId, AdTile> = demo_ads
+            .clone()
+            .into_iter()
+            .filter_map(|(k, v)| Some((PlacementId(k), v.into_iter().next()?)))
+            .collect();
+        let first_key = demo_ads
+            .iter()
+            .next()
+            .expect("No test data in `get_example_happy_uatile_response`")
+            .0;
+
+        ads_store.store_ads::<AdTile>(demo_ads.clone(), one_min_ago);
+        assert!(
+            ads_store.get_stored_ads::<AdTile>(first_key).is_none(),
+            "Old data past TTL date must not be returned."
+        );
+
+        ads_store.store_ads::<AdTile>(demo_ads.clone(), five_sec_ago);
+        assert!(
+            ads_store.get_stored_ads::<AdTile>(first_key).is_some(),
+            "Could not fetch fresh ad from ads store."
+        );
+    }
+}
diff --git a/components/ads-client/src/client.rs b/components/ads-client/src/client.rs
index 6f510c55617..4c43a30665e 100644
--- a/components/ads-client/src/client.rs
+++ b/components/ads-client/src/client.rs
@@ -6,6 +6,7 @@
 use std::collections::HashMap;
 use std::time::Duration;
 
+use crate::ads_store::{AdsStorable, AdsStore, PlacementId};
 use crate::http_cache::{ByteSize, CachePolicy, HttpCache};
 use crate::mars::ad_request::{AdPlacementRequest, AdRequestFlags};
 use crate::mars::ad_response::{AdImage, AdResponse, AdResponseValue, AdSpoc, AdTile};
@@ -42,6 +43,7 @@ where
     client: MARSClient<T>,
     context_id_provider: Box<dyn ContextIdProvider>,
     telemetry: T,
+    ads_store: AdsStore,
 }
 
 impl<T> AdsClient<T>
@@ -91,6 +93,7 @@ where
             client,
             context_id_provider,
             telemetry: telemetry.clone(),
+            ads_store: AdsStore::new(),
         }
     }
 
@@ -110,6 +113,20 @@ where
         Ok(())
     }
 
+    #[allow(dead_code)]
+    pub fn store_ads<A: AdsStorable>(&mut self, ads: HashMap<PlacementId, A::StorageType>) {
+        let now = std::time::Instant::now();
+        self.ads_store.store_ads::<A>(ads, now);
+    }
+
+    #[allow(dead_code)]
+    pub fn get_stored_ads<A: AdsStorable>(
+        &self,
+        placement_id: &PlacementId,
+    ) -> Option<&A::StorageType> {
+        self.ads_store.get_stored_ads::<A>(placement_id)
+    }
+
     pub fn get_context_id(&self) -> context_id::ApiResult<String> {
         self.context_id_provider.context_id()
     }
@@ -301,6 +318,7 @@ mod tests {
                 Box::new(DefaultContextIdCallback),
             )),
             telemetry,
+            ads_store: AdsStore::new(),
         }
     }
 
diff --git a/components/ads-client/src/lib.rs b/components/ads-client/src/lib.rs
index 87cecb2a5f8..b3aab4381d1 100644
--- a/components/ads-client/src/lib.rs
+++ b/components/ads-client/src/lib.rs
@@ -15,6 +15,8 @@ use client::AdsClient;
 use error_support::error;
 use http_cache::CachePolicy;
 use mars::ad_request::{AdPlacementRequest, AdRequestFlags};
+
+pub mod ads_store;
 mod client;
 mod ffi;
 pub mod http_cache;