diff --git a/src/data/account/mem.rs b/src/data/account/mem.rs
new file mode 100644
index 0000000..0313d13
--- /dev/null
+++ b/src/data/account/mem.rs
@@ -0,0 +1,30 @@
+use crate::core::*;
+
+use crate::data::memcache::{GetId, MemCache};
+use crate::model::Account;
+
+pub struct MemAccountDataSource {
+    cache: MemCache<Id, Account>,
+}
+
+impl MemAccountDataSource {
+    pub fn new() -> MemAccountDataSource {
+        MemAccountDataSource {
+            cache: MemCache::new(),
+        }
+    }
+
+    pub async fn by_id(&self, id: Id) -> Option<Account> {
+        self.cache.get(id).await
+    }
+
+    pub async fn store(&self, account: Account) {
+        self.cache.put(account).await
+    }
+}
+
+impl GetId<Id> for Account {
+    fn get_id(&self) -> Id {
+        self.id
+    }
+}
diff --git a/src/data/account/mod.rs b/src/data/account/mod.rs
index 1b4d041..d751623 100644
--- a/src/data/account/mod.rs
+++ b/src/data/account/mod.rs
@@ -1,3 +1,5 @@
+mod mem;
 mod pg;
 
+pub use mem::MemAccountDataSource;
 pub use pg::PgAccountDataSource;
diff --git a/src/data/memcache.rs b/src/data/memcache.rs
new file mode 100644
index 0000000..ed9b173
--- /dev/null
+++ b/src/data/memcache.rs
@@ -0,0 +1,95 @@
+use std::marker::PhantomData;
+use tokio::sync::RwLock;
+use uuid::Uuid;
+
+use crate::core::*;
+
+/// Shared in-memory LRU with multiple cache lines.
+pub struct MemCache<I: IndexableId, T: GetId<I> + Clone> {
+    lines: Vec<RwLock<Option<T>>>,
+    _phantom: PhantomData<I>,
+}
+
+pub trait GetId<I: IndexableId> {
+    fn get_id(&self) -> I;
+}
+
+pub trait IndexableId: Eq {
+    fn compute_index(&self, modulus: usize) -> usize;
+}
+
+impl<I: IndexableId, T: GetId<I> + Clone> MemCache<I, T> {
+    pub fn new() -> MemCache<I, T> {
+        MemCache::with_capacity(256)
+    }
+
+    pub fn with_capacity(capacity: usize) -> MemCache<I, T> {
+        assert!(capacity > 0);
+        let mut lines = Vec::with_capacity(capacity);
+        for _ in 0..capacity {
+            lines.push(RwLock::new(None));
+        }
+        MemCache { lines, _phantom: PhantomData }
+    }
+
+    pub async fn get(&self, id: I) -> Option<T> {
+        let index = id.compute_index(self.lines.len());
+        let guard = self.lines[index].read().await;
+        let entry = guard.as_ref()?;
+        if entry.get_id() == id {
+            Some(entry.clone())
+        } else {
+            None
+        }
+    }
+
+    pub async fn put(&self, entry: T) {
+        let index = entry.get_id().compute_index(self.lines.len());
+        let mut guard = self.lines[index].write().await;
+        *guard = Some(entry);
+    }
+}
+
+impl IndexableId for Id {
+    fn compute_index(&self, modulus: usize) -> usize {
+        *self as usize % modulus
+    }
+}
+
+impl IndexableId for Uuid {
+    fn compute_index(&self, modulus: usize) -> usize {
+        self.as_u128() as usize % modulus
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[derive(Clone, Debug, PartialEq)]
+    struct TestEntry {
+        id: Id,
+    }
+
+    impl GetId<Id> for TestEntry {
+        fn get_id(&self) -> Id {
+            self.id
+        }
+    }
+
+    #[actix_web::test]
+    async fn store_stuff() {
+        let cache = MemCache::with_capacity(256);
+        for id in 0..256 {
+            let entry = TestEntry { id };
+            cache.put(entry.clone()).await;
+            assert_eq!(cache.get(id).await, Some(entry));
+        }
+        for id in 256..512 {
+            let entry = TestEntry { id };
+            cache.put(entry.clone()).await;
+            assert_eq!(cache.get(id - 256).await, None);
+            assert_eq!(cache.get(id).await, Some(entry));
+        }
+    }
+}
diff --git a/src/data/mod.rs b/src/data/mod.rs
index 4e68b81..a2e1603 100644
--- a/src/data/mod.rs
+++ b/src/data/mod.rs
@@ -1,3 +1,6 @@
+/// Small support utility for in-memory cache.
+pub mod memcache;
+
 pub mod account;
 pub mod follow;
 pub mod like;
diff --git a/src/data/note/mem.rs b/src/data/note/mem.rs
new file mode 100644
index 0000000..592b2c1
--- /dev/null
+++ b/src/data/note/mem.rs
@@ -0,0 +1,30 @@
+use crate::core::*;
+
+use crate::data::memcache::{GetId, MemCache};
+use crate::model::Note;
+
+pub struct MemNoteDataSource {
+    cache: MemCache<Id, Note>,
+}
+
+impl MemNoteDataSource {
+    pub fn new() -> MemNoteDataSource {
+        MemNoteDataSource {
+            cache: MemCache::new(),
+        }
+    }
+
+    pub async fn by_id(&self, id: Id) -> Option<Note> {
+        self.cache.get(id).await
+    }
+
+    pub async fn store(&self, note: Note) {
+        self.cache.put(note).await
+    }
+}
+
+impl GetId<Id> for Note {
+    fn get_id(&self) -> Id {
+        self.id
+    }
+}
diff --git a/src/data/note/mod.rs b/src/data/note/mod.rs
index 74388aa..f496350 100644
--- a/src/data/note/mod.rs
+++ b/src/data/note/mod.rs
@@ -1,3 +1,5 @@
+mod mem;
 mod pg;
 
+pub use mem::MemNoteDataSource;
 pub use pg::PgNoteDataSource;
diff --git a/src/data/object/mem.rs b/src/data/object/mem.rs
new file mode 100644
index 0000000..de1f51a
--- /dev/null
+++ b/src/data/object/mem.rs
@@ -0,0 +1,30 @@
+use uuid::Uuid;
+
+use crate::data::memcache::{GetId, MemCache};
+use crate::model::Object;
+
+pub struct MemObjectDataSource {
+    cache: MemCache<Uuid, Object>,
+}
+
+impl MemObjectDataSource {
+    pub fn new() -> MemObjectDataSource {
+        MemObjectDataSource {
+            cache: MemCache::new(),
+        }
+    }
+
+    pub async fn by_id(&self, id: Uuid) -> Option<Object> {
+        self.cache.get(id).await
+    }
+
+    pub async fn store(&self, obj: Object) {
+        self.cache.put(obj).await
+    }
+}
+
+impl GetId<Uuid> for Object {
+    fn get_id(&self) -> Uuid {
+        self.id
+    }
+}
diff --git a/src/data/object/mod.rs b/src/data/object/mod.rs
index 568fa16..e1d08ee 100644
--- a/src/data/object/mod.rs
+++ b/src/data/object/mod.rs
@@ -1,3 +1,5 @@
-pub mod pg;
+mod mem;
+mod pg;
 
+pub use mem::MemObjectDataSource;
 pub use pg::PgObjectDataSource;
diff --git a/src/data/user/mem.rs b/src/data/user/mem.rs
new file mode 100644
index 0000000..81ce8f1
--- /dev/null
+++ b/src/data/user/mem.rs
@@ -0,0 +1,30 @@
+use crate::core::*;
+
+use crate::data::memcache::{GetId, MemCache};
+use crate::model::User;
+
+pub struct MemUserDataSource {
+    cache: MemCache<Id, User>,
+}
+
+impl MemUserDataSource {
+    pub fn new() -> MemUserDataSource {
+        MemUserDataSource {
+            cache: MemCache::new(),
+        }
+    }
+
+    pub async fn by_id(&self, id: Id) -> Option<User> {
+        self.cache.get(id).await
+    }
+
+    pub async fn store(&self, user: User) {
+        self.cache.put(user).await
+    }
+}
+
+impl GetId<Id> for User {
+    fn get_id(&self) -> Id {
+        self.id
+    }
+}
diff --git a/src/data/user/mod.rs b/src/data/user/mod.rs
index 05bd283..c2eb77a 100644
--- a/src/data/user/mod.rs
+++ b/src/data/user/mod.rs
@@ -1,3 +1,5 @@
-pub mod pg;
+mod mem;
+mod pg;
 
+pub use mem::MemUserDataSource;
 pub use pg::PgUserDataSource;
diff --git a/src/model/account.rs b/src/model/account.rs
index 3ef5f4a..c615f56 100644
--- a/src/model/account.rs
+++ b/src/model/account.rs
@@ -5,7 +5,7 @@ use sqlx::FromRow;
 use crate::core::Id;
 use crate::util::validate::{ResultBuilder, Validate};
 
-#[derive(Deserialize, Serialize, FromRow)]
+#[derive(Clone, Deserialize, Serialize, FromRow)]
 pub struct Account {
     pub id: Id,
     pub iri: Option<String>,
diff --git a/src/model/note.rs b/src/model/note.rs
index b463198..5cc7b7f 100644
--- a/src/model/note.rs
+++ b/src/model/note.rs
@@ -4,7 +4,7 @@ use sqlx::FromRow;
 
 use crate::core::*;
 
-#[derive(Deserialize, Serialize, FromRow)]
+#[derive(Clone, Deserialize, Serialize, FromRow)]
 pub struct Note {
     pub id: Id,
     pub account_id: Id,
diff --git a/src/model/object.rs b/src/model/object.rs
index b30784c..4d1a872 100644
--- a/src/model/object.rs
+++ b/src/model/object.rs
@@ -2,7 +2,7 @@ use chrono::NaiveDateTime;
 use sqlx::types::Uuid;
 use sqlx::FromRow;
 
-#[derive(FromRow)]
+#[derive(Clone, FromRow)]
 pub struct Object {
     pub id: Uuid,
     pub iri: String,
diff --git a/src/model/user.rs b/src/model/user.rs
index b88a8ad..f782fa2 100644
--- a/src/model/user.rs
+++ b/src/model/user.rs
@@ -4,7 +4,7 @@ use sqlx::FromRow;
 use crate::core::*;
 use crate::util::validate::{ResultBuilder, Validate};
 
-#[derive(Deserialize, Serialize, FromRow)]
+#[derive(Clone, Deserialize, Serialize, FromRow)]
 pub struct User {
     pub id: Id,
     pub account_id: Id,
diff --git a/src/repo/account.rs b/src/repo/account.rs
index 9291fae..aa451be 100644
--- a/src/repo/account.rs
+++ b/src/repo/account.rs
@@ -1,17 +1,19 @@
 use sqlx::PgPool;
 
 use crate::core::*;
-use crate::data::account::PgAccountDataSource;
+use crate::data::account::{MemAccountDataSource, PgAccountDataSource};
 use crate::model::account::{Account, NewAccount};
 
 pub struct AccountRepo {
     db: PgAccountDataSource,
+    mem: MemAccountDataSource,
 }
 
 impl AccountRepo {
     pub fn new(db_pool: PgPool) -> AccountRepo {
         AccountRepo {
             db: PgAccountDataSource::new(db_pool),
+            mem: MemAccountDataSource::new(),
         }
     }
 
@@ -19,7 +21,11 @@ impl AccountRepo {
     where
         I: Into<Id> + Send,
     {
-        self.db.by_id(id.into()).await
+        let id = id.into();
+        match self.mem.by_id(id).await {
+            Some(account) => Ok(account),
+            None => self.db.by_id(id).await,
+        }
     }
 
     pub async fn create<T, E>(&self, new: T) -> Result<Account>
@@ -28,6 +34,8 @@ impl AccountRepo {
         E: Into<Error>,
     {
         let new = new.try_into().map_err(|e| e.into())?.inner();
-        self.db.create(new).await
+        let account = self.db.create(new).await?;
+        self.mem.store(account.clone()).await;
+        Ok(account)
     }
 }
diff --git a/src/repo/note.rs b/src/repo/note.rs
index 974c0c5..384323b 100644
--- a/src/repo/note.rs
+++ b/src/repo/note.rs
@@ -2,17 +2,19 @@ use chrono::NaiveDateTime;
 use sqlx::PgPool;
 
 use crate::core::*;
-use crate::data::PgNoteDataSource;
+use crate::data::{MemNoteDataSource, PgNoteDataSource};
 use crate::model::{NewNote, Note};
 
 pub struct NoteRepo {
     db: PgNoteDataSource,
+    mem: MemNoteDataSource,
 }
 
 impl NoteRepo {
     pub fn new(db_pool: PgPool) -> NoteRepo {
         NoteRepo {
             db: PgNoteDataSource::new(db_pool),
+            mem: MemNoteDataSource::new(),
         }
     }
 
@@ -20,7 +22,11 @@ impl NoteRepo {
     where
         I: Into<Id> + Send,
     {
-        self.db.by_id(id.into()).await
+        let id = id.into();
+        match self.mem.by_id(id).await {
+            Some(note) => Ok(note),
+            None => self.db.by_id(id).await,
+        }
     }
 
     pub async fn by_account<I>(&self, account_id: I, since: NaiveDateTime) -> Result<Vec<Note>>
@@ -36,6 +42,8 @@ impl NoteRepo {
         E: Into<Error>,
     {
         let new = new.try_into().map_err(|e| e.into())?.inner();
-        self.db.create(new).await
+        let note = self.db.create(new).await?;
+        self.mem.store(note.clone()).await;
+        Ok(note)
     }
 }
diff --git a/src/repo/object.rs b/src/repo/object.rs
index c82f79e..a445730 100644
--- a/src/repo/object.rs
+++ b/src/repo/object.rs
@@ -2,22 +2,26 @@ use sqlx::types::Uuid;
 use sqlx::PgPool;
 
 use crate::core::*;
-use crate::data::object::PgObjectDataSource;
+use crate::data::object::{MemObjectDataSource, PgObjectDataSource};
 use crate::model::{NewObject, Object};
 
 pub struct ObjectRepo {
     db: PgObjectDataSource,
+    mem: MemObjectDataSource,
 }
 
 impl ObjectRepo {
     pub fn new(db_pool: PgPool) -> ObjectRepo {
         ObjectRepo {
             db: PgObjectDataSource::new(db_pool),
+            mem: MemObjectDataSource::new(),
         }
     }
 
     pub async fn create(&self, new: NewObject) -> Result<Object> {
-        self.db.create(new).await
+        let obj = self.db.create(new).await?;
+        self.mem.store(obj.clone()).await;
+        Ok(obj)
     }
 
     pub async fn update<T, E>(&self, object: T) -> Result<Object>
@@ -35,7 +39,11 @@ impl ObjectRepo {
     where
         U: Into<Uuid>,
     {
-        self.db.by_id(id.into()).await
+        let id = id.into();
+        match self.mem.by_id(id).await {
+            Some(obj) => Ok(obj),
+            None => self.db.by_id(id).await,
+        }
     }
 
     pub async fn by_iri(&self, iri: &str) -> Result<Object> {
diff --git a/src/repo/user.rs b/src/repo/user.rs
index fd1820f..495e4fb 100644
--- a/src/repo/user.rs
+++ b/src/repo/user.rs
@@ -1,17 +1,19 @@
 use sqlx::PgPool;
 
 use crate::core::*;
-use crate::data::user::PgUserDataSource;
+use crate::data::user::{MemUserDataSource, PgUserDataSource};
 use crate::model::user::{NewUser, User};
 
 pub struct UserRepo {
     db: PgUserDataSource,
+    mem: MemUserDataSource,
 }
 
 impl UserRepo {
     pub fn new(db_pool: PgPool) -> UserRepo {
         UserRepo {
             db: PgUserDataSource::new(db_pool),
+            mem: MemUserDataSource::new(),
         }
     }
 
@@ -19,7 +21,11 @@ impl UserRepo {
     where
         I: Into<Id> + Send,
     {
-        self.db.by_id(id.into()).await
+        let id = id.into();
+        match self.mem.by_id(id).await {
+            Some(user) => Ok(user),
+            None => self.db.by_id(id).await,
+        }
     }
 
     pub async fn by_account<I>(&self, account_id: I) -> Result<User>
@@ -41,8 +47,9 @@ impl UserRepo {
         T: TryInto<Sane<NewUser>, Error = E> + Send,
         E: Into<Error>,
     {
-        self.db
-            .create(new.try_into().map_err(|e| e.into())?.inner())
-            .await
+        let new = new.try_into().map_err(|e| e.into())?.inner();
+        let user = self.db.create(new).await?;
+        self.mem.store(user.clone()).await;
+        Ok(user)
     }
 }