diff --git a/Cargo.toml b/Cargo.toml
index 67f151d1f..e73a41cba 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,9 +5,7 @@ members = [
     "bindings/nostr-sdk-ffi",
     "bindings/nostr-sdk-js",
     "bindings/uniffi-bindgen",
-    "crates/nostr",
-    "crates/nostr-sdk",
-    "crates/nostr-sdk-net",
+    "crates/*",
 ]
 default-members = ["crates/*"]
 resolver = "2"
diff --git a/crates/nostr-sdk-db/Cargo.toml b/crates/nostr-sdk-db/Cargo.toml
new file mode 100644
index 000000000..36ebc56c1
--- /dev/null
+++ b/crates/nostr-sdk-db/Cargo.toml
@@ -0,0 +1,18 @@
+[package]
+name = "nostr-sdk-db"
+version = "0.1.0"
+edition = "2021"
+description = "Nostr SDK Database"
+authors = ["Yuki Kishimoto <yukikishimoto@protonmail.com>"]
+homepage.workspace = true
+repository.workspace = true
+license.workspace = true
+readme = "README.md"
+rust-version.workspace = true
+keywords = ["nostr", "sdk", "db"]
+
+[dependencies]
+async-trait = "0.1"
+nostr = { version = "0.24", path = "../nostr", default-features = false, features = ["std"] }
+thiserror = { workspace = true }
+tokio = { workspace = true, features = ["sync"] }
diff --git a/crates/nostr-sdk-db/src/error.rs b/crates/nostr-sdk-db/src/error.rs
new file mode 100644
index 000000000..95209a2f2
--- /dev/null
+++ b/crates/nostr-sdk-db/src/error.rs
@@ -0,0 +1,27 @@
+// Copyright (c) 2022-2023 Yuki Kishimoto
+// Distributed under the MIT software license
+
+//! Database Error
+
+use thiserror::Error;
+
+/// Database Error
+#[derive(Debug, Error)]
+pub enum DatabaseError {
+    /// An error happened in the underlying database backend.
+    #[error(transparent)]
+    Backend(Box<dyn std::error::Error + Send + Sync>),
+}
+
+impl DatabaseError {
+    /// Create a new [`Backend`][Self::Backend] error.
+    ///
+    /// Shorthand for `Error::Backend(Box::new(error))`.
+    #[inline]
+    pub fn backend<E>(error: E) -> Self
+    where
+        E: std::error::Error + Send + Sync + 'static,
+    {
+        Self::Backend(Box::new(error))
+    }
+}
diff --git a/crates/nostr-sdk-db/src/lib.rs b/crates/nostr-sdk-db/src/lib.rs
new file mode 100644
index 000000000..e10466dd4
--- /dev/null
+++ b/crates/nostr-sdk-db/src/lib.rs
@@ -0,0 +1,102 @@
+// Copyright (c) 2022-2023 Yuki Kishimoto
+// Distributed under the MIT software license
+
+//! Nostr SDK Database
+
+#![warn(missing_docs)]
+#![warn(rustdoc::bare_urls)]
+
+use async_trait::async_trait;
+use nostr::{Event, EventId, Filter, Url};
+
+mod error;
+pub mod memory;
+
+pub use self::error::DatabaseError;
+
+/// Backend
+pub enum Backend {
+    /// Memory
+    Memory,
+    /// RocksDB
+    RocksDB,
+    /// Lightning Memory-Mapped Database
+    LMDB,
+    /// SQLite
+    SQLite,
+    /// IndexedDB
+    IndexedDB,
+    /// Custom
+    Custom(String),
+}
+
+/// A type-erased [`StateStore`].
+pub type DynNostrDatabase = dyn NostrDatabase<Err = DatabaseError>;
+
+/// Nostr SDK Database
+#[async_trait]
+pub trait NostrDatabase: AsyncTraitDeps {
+    /// Error
+    type Err;
+
+    /// Name of the backend database used (ex. rocksdb, lmdb, sqlite, indexeddb, ...)
+    fn backend(&self) -> Backend;
+
+    /// Save [`Event`] into store
+    async fn save_event(&self, event: &Event) -> Result<(), Self::Err>;
+
+    /// Save [`EventId`] seen by relay
+    ///
+    /// Useful for NIP65 (gossip)
+    async fn save_event_id_seen_by_relay(
+        &self,
+        event_id: EventId,
+        relay_url: Url,
+    ) -> Result<(), Self::Err>;
+
+    /// Get list of relays that have seen the [`EventId`]
+    async fn event_recently_seen_on_relays(&self, event_id: EventId)
+        -> Result<Vec<Url>, Self::Err>;
+
+    /// Query store with filters
+    async fn query(&self, filters: Vec<Filter>) -> Result<Vec<Event>, Self::Err>;
+
+    /// Get event IDs by filters
+    ///
+    /// Uuseful for negentropy reconciliation
+    async fn event_ids_by_filters(&self, filters: Vec<Filter>) -> Result<Vec<EventId>, Self::Err>;
+}
+
+/// Alias for `Send` on non-wasm, empty trait (implemented by everything) on
+/// wasm.
+#[cfg(not(target_arch = "wasm32"))]
+pub trait SendOutsideWasm: Send {}
+#[cfg(not(target_arch = "wasm32"))]
+impl<T: Send> SendOutsideWasm for T {}
+
+/// Alias for `Send` on non-wasm, empty trait (implemented by everything) on
+/// wasm.
+#[cfg(target_arch = "wasm32")]
+pub trait SendOutsideWasm {}
+#[cfg(target_arch = "wasm32")]
+impl<T> SendOutsideWasm for T {}
+
+/// Alias for `Sync` on non-wasm, empty trait (implemented by everything) on
+/// wasm.
+#[cfg(not(target_arch = "wasm32"))]
+pub trait SyncOutsideWasm: Sync {}
+#[cfg(not(target_arch = "wasm32"))]
+impl<T: Sync> SyncOutsideWasm for T {}
+
+/// Alias for `Sync` on non-wasm, empty trait (implemented by everything) on
+/// wasm.
+#[cfg(target_arch = "wasm32")]
+pub trait SyncOutsideWasm {}
+#[cfg(target_arch = "wasm32")]
+impl<T> SyncOutsideWasm for T {}
+
+/// Super trait that is used for our store traits, this trait will differ if
+/// it's used on WASM. WASM targets will not require `Send` and `Sync` to have
+/// implemented, while other targets will.
+pub trait AsyncTraitDeps: std::fmt::Debug + SendOutsideWasm + SyncOutsideWasm {}
+impl<T: std::fmt::Debug + SendOutsideWasm + SyncOutsideWasm> AsyncTraitDeps for T {}
diff --git a/crates/nostr-sdk-db/src/memory.rs b/crates/nostr-sdk-db/src/memory.rs
new file mode 100644
index 000000000..2119f6a6a
--- /dev/null
+++ b/crates/nostr-sdk-db/src/memory.rs
@@ -0,0 +1,84 @@
+// Copyright (c) 2022-2023 Yuki Kishimoto
+// Distributed under the MIT software license
+
+//! Nostr SDK Database
+
+use std::collections::{HashMap, HashSet};
+use std::sync::Arc;
+
+use async_trait::async_trait;
+use nostr::{Event, EventId, Filter, Url};
+use thiserror::Error;
+use tokio::sync::RwLock;
+
+use crate::{Backend, DatabaseError, NostrDatabase};
+
+/// Memory Database Error
+#[derive(Debug, Error)]
+pub enum Error {}
+
+impl From<Error> for DatabaseError {
+    fn from(e: Error) -> Self {
+        DatabaseError::backend(e)
+    }
+}
+
+/// Memory Database (RAM)
+#[derive(Debug, Default)]
+pub struct MemoryDatabase {
+    seen_event_ids: Arc<RwLock<HashMap<EventId, HashSet<Url>>>>,
+}
+
+impl MemoryDatabase {
+    /// New Memory database
+    pub fn new() -> Self {
+        Self::default()
+    }
+}
+
+#[async_trait]
+impl NostrDatabase for MemoryDatabase {
+    type Err = DatabaseError;
+
+    fn backend(&self) -> Backend {
+        Backend::Memory
+    }
+
+    async fn save_event(&self, _event: &Event) -> Result<(), Self::Err> {
+        Ok(())
+    }
+
+    async fn save_event_id_seen_by_relay(
+        &self,
+        event_id: EventId,
+        relay_url: Url,
+    ) -> Result<(), Self::Err> {
+        let mut seen_event_ids = self.seen_event_ids.write().await;
+        seen_event_ids
+            .entry(event_id)
+            .and_modify(|set| {
+                set.insert(relay_url.clone());
+            })
+            .or_insert_with(|| {
+                let mut set = HashSet::with_capacity(1);
+                set.insert(relay_url);
+                set
+            });
+        Ok(())
+    }
+
+    async fn event_recently_seen_on_relays(
+        &self,
+        _event_id: EventId,
+    ) -> Result<Vec<Url>, Self::Err> {
+        todo!()
+    }
+
+    async fn query(&self, _filters: Vec<Filter>) -> Result<Vec<Event>, Self::Err> {
+        Ok(Vec::new())
+    }
+
+    async fn event_ids_by_filters(&self, _filters: Vec<Filter>) -> Result<Vec<EventId>, Self::Err> {
+        Ok(Vec::new())
+    }
+}