diff --git a/README.md b/README.md
index 9423ad9..25fb5fa 100644
--- a/README.md
+++ b/README.md
@@ -14,6 +14,7 @@ Some general-purpose utilities used elsewhere in paravel.
 - `LRUCache` is an implementation of an LRU cache.
 - `Worker` is an implementation of an asynchronous queue.
 - `Tools` is a collection of general-purpose utility functions.
+- `Store` is an implementation of svelte-like subscribable stores with extra features.
 
 ## @coracle.social/util
 
diff --git a/package-lock.json b/package-lock.json
index 88d6afe..a04ef00 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -391,6 +391,12 @@
       "integrity": "sha512-I8EUhyrgfLrcTkzV3TSsGyl1tSuPrEDzr0yd5m90UgNxQkyDXULk3b6MlQqTCpZpNtWe1K0hzclnZkTcLBe2UQ==",
       "dev": true
     },
+    "node_modules/@types/throttle-debounce": {
+      "version": "5.0.2",
+      "resolved": "https://registry.npmjs.org/@types/throttle-debounce/-/throttle-debounce-5.0.2.tgz",
+      "integrity": "sha512-pDzSNulqooSKvSNcksnV72nk8p7gRqN8As71Sp28nov1IgmPKWbOEIwAWvBME5pPTtaXJAvG3O4oc76HlQ4kqQ==",
+      "dev": true
+    },
     "node_modules/@typescript-eslint/eslint-plugin": {
       "version": "5.62.0",
       "resolved": "https://registry.npmjs.org/@typescript-eslint/eslint-plugin/-/eslint-plugin-5.62.0.tgz",
@@ -3029,6 +3035,14 @@
       "integrity": "sha512-N+8UisAXDGk8PFXP4HAzVR9nbfmVJ3zYLAWiTIoqC5v5isinhr+r5uaO8+7r3BMfuNIufIsA7RdpVgacC2cSpw==",
       "dev": true
     },
+    "node_modules/throttle-debounce": {
+      "version": "5.0.0",
+      "resolved": "https://registry.npmjs.org/throttle-debounce/-/throttle-debounce-5.0.0.tgz",
+      "integrity": "sha512-2iQTSgkkc1Zyk0MeVrt/3BvuOXYPl/R8Z0U2xxo9rjwNciaHDG3R+Lm6dh4EeUci49DanvBnuqI6jshoQQRGEg==",
+      "engines": {
+        "node": ">=12.22"
+      }
+    },
     "node_modules/through": {
       "version": "2.3.8",
       "resolved": "https://registry.npmjs.org/through/-/through-2.3.8.tgz",
@@ -3323,10 +3337,12 @@
       "version": "0.0.1",
       "license": "MIT",
       "dependencies": {
-        "@scure/base": "^1.1.6"
+        "@scure/base": "^1.1.6",
+        "throttle-debounce": "^5.0.0"
       },
       "devDependencies": {
         "@types/events": "^3.0.3",
+        "@types/throttle-debounce": "^5.0.2",
         "gts": "^5.0.1",
         "tsc-multi": "^1.1.0",
         "typescript": "~5.1.6"
diff --git a/packages/lib/Fluent.ts b/packages/lib/Fluent.ts
index 4d1e747..238d87e 100644
--- a/packages/lib/Fluent.ts
+++ b/packages/lib/Fluent.ts
@@ -55,6 +55,8 @@ export class Fluent<T> {
 
   forEach = (f: (t: T, i: number) => void) => this.xs.forEach(f)
 
+  join = (s: string) => this.valueOf().join(s)
+
   set = (i: number, x: T) => this.clone([...this.xs.slice(0, i), x, ...this.xs.slice(i + 1)])
 
   concat = (xs: T[]) => this.clone(this.xs.concat(xs))
diff --git a/packages/lib/Store.ts b/packages/lib/Store.ts
new file mode 100644
index 0000000..7a4f9e3
--- /dev/null
+++ b/packages/lib/Store.ts
@@ -0,0 +1,329 @@
+import {throttle} from "throttle-debounce"
+import {ensurePlural, identity} from "./Tools"
+
+type Invalidator<T> = (value?: T) => void
+type Derivable = Readable<any> | Readable<any>[]
+type Subscriber<T> = (value: T) => void
+type Unsubscriber = () => void
+type R = Record<string, any>
+type M<T> = Map<string, T>
+
+export interface Readable<T> {
+  get: () => T
+  subscribe(this: void, run: Subscriber<T>, invalidate?: Invalidator<T>): Unsubscriber
+  derived: <U>(f: (v: T) => U) => Readable<U>
+  throttle(t: number): Readable<T>
+}
+
+export class Writable<T> implements Readable<T> {
+  private value: T
+  private subs: Subscriber<T>[] = []
+
+  constructor(defaultValue: T, t?: number) {
+    this.value = defaultValue
+
+    if (t) {
+      this.notify = throttle(t, this.notify)
+    }
+  }
+
+  notify = () => {
+    for (const sub of this.subs) {
+      sub(this.value)
+    }
+  }
+
+  get() {
+    return this.value
+  }
+
+  set(newValue: T) {
+    this.value = newValue
+    this.notify()
+  }
+
+  update(f: (v: T) => T) {
+    this.set(f(this.value))
+  }
+
+  async updateAsync(f: (v: T) => Promise<T>) {
+    this.set(await f(this.value))
+  }
+
+  subscribe(f: Subscriber<T>) {
+    this.subs.push(f)
+
+    f(this.value)
+
+    return () => {
+      this.subs.splice(this.subs.findIndex(x => x === f), 1)
+    }
+  }
+
+  derived<U>(f: (v: T) => U): Derived<U> {
+    return new Derived<U>(this, f)
+  }
+
+  throttle = (t: number): Derived<T> => {
+    return new Derived<T>(this, identity, t)
+  }
+}
+
+export class Derived<T> implements Readable<T> {
+  private callerSubs: Subscriber<T>[] = []
+  private mySubs: Unsubscriber[] = []
+  private stores: Derivable
+  private getValue: (values: any) => T
+  private latestValue: T | undefined
+
+  constructor(stores: Derivable, getValue: (values: any) => T, t = 0) {
+    this.stores = stores
+    this.getValue = getValue
+
+    if (t) {
+      this.notify = throttle(t, this.notify)
+    }
+  }
+
+  notify = () => {
+    this.latestValue = undefined
+    this.callerSubs.forEach(f => f(this.get()))
+  }
+
+  getInput() {
+    if (Array.isArray(this.stores)) {
+      return this.stores.map(s => s.get())
+    } else {
+      return this.stores.get()
+    }
+  }
+
+  get = (): T => {
+    // Recalculate if we're not subscribed, because we won't get notified when deps change
+    if (this.latestValue === undefined || this.mySubs.length === 0) {
+      this.latestValue = this.getValue(this.getInput())
+    }
+
+    return this.latestValue
+  }
+
+  subscribe(f: Subscriber<T>) {
+    if (this.callerSubs.length === 0) {
+      for (const s of ensurePlural(this.stores)) {
+        this.mySubs.push(s.subscribe(this.notify))
+      }
+    }
+
+    this.callerSubs.push(f)
+
+    f(this.get())
+
+    return () => {
+      this.callerSubs.splice(this.callerSubs.findIndex(x => x === f), 1)
+
+      if (this.callerSubs.length === 0) {
+        for (const unsub of this.mySubs.splice(0)) {
+          unsub()
+        }
+      }
+    }
+  }
+
+  derived<U>(f: (v: T) => U): Readable<U> {
+    return new Derived(this, f) as Readable<U>
+  }
+
+  throttle = (t: number): Readable<T> => {
+    return new Derived<T>(this, identity, t)
+  }
+}
+
+export class Key<T extends R> implements Readable<T> {
+  readonly pk: string
+  readonly key: string
+  private base: Writable<M<T>>
+  private store: Readable<T>
+
+  constructor(base: Writable<M<T>>, pk: string, key: string) {
+    if (!(base.get() instanceof Map)) {
+      throw new Error("`key` can only be used on map collections")
+    }
+
+    this.pk = pk
+    this.key = key
+    this.base = base
+    this.store = base.derived<T>(m => m.get(key) as T)
+  }
+
+  get = () => this.base.get().get(this.key) as T
+
+  subscribe = (f: Subscriber<T>) => this.store.subscribe(f)
+
+  derived = <U>(f: (v: T) => U) => this.store.derived<U>(f)
+
+  throttle = (t: number) => this.store.throttle(t)
+
+  exists = () => this.base.get().has(this.key)
+
+  update = (f: (v: T) => T) =>
+    this.base.update((m: M<T>) => {
+      if (!this.key) {
+        throw new Error(`Cannot set key: "${this.key}"`)
+      }
+
+      // Make sure the pk always get set on the record
+      const {pk, key} = this
+      const oldValue = {...m.get(key), [pk]: key} as T
+      const newValue = {...f(oldValue), [pk]: key}
+
+      m.set(this.key, newValue)
+
+      return m
+    })
+
+  set = (v: T) => this.update(() => v)
+
+  merge = (d: Partial<T>) => this.update(v => ({...v, ...d}))
+
+  remove = () =>
+    this.base.update(m => {
+      m.delete(this.key)
+
+      return m
+    })
+
+  pop = () => {
+    const v = this.get()
+
+    this.remove()
+
+    return v
+  }
+}
+
+export class DerivedKey<T extends R> implements Readable<T> {
+  readonly pk: string
+  readonly key: string
+  private base: Readable<M<T>>
+  private store: Readable<T>
+
+  constructor(base: Readable<M<T>>, pk: string, key: string) {
+    if (!(base.get() instanceof Map)) {
+      throw new Error("`key` can only be used on map collections")
+    }
+
+    this.pk = pk
+    this.key = key
+    this.base = base
+    this.store = base.derived<T>(m => m.get(key) as T)
+  }
+
+  get = () => this.base.get().get(this.key) as T
+
+  subscribe = (f: Subscriber<T>) => this.store.subscribe(f)
+
+  derived = <U>(f: (v: T) => U) => this.store.derived<U>(f)
+
+  throttle = (t: number) => this.store.throttle(t)
+
+  exists = () => this.base.get().has(this.key)
+}
+
+export class Collection<T extends R> implements Readable<T[]> {
+  readonly pk: string
+  readonly mapStore: Writable<M<T>>
+  readonly listStore: Readable<T[]>
+
+  constructor(pk: string, t?: number) {
+    this.pk = pk
+    this.mapStore = writable(new Map())
+    this.listStore = this.mapStore.derived<T[]>((m: M<T>) => Array.from(m.values()))
+
+    if (t) {
+      this.mapStore.notify = throttle(t, this.mapStore.notify)
+    }
+  }
+
+  get = () => this.listStore.get()
+
+  getMap = () => this.mapStore.get()
+
+  subscribe = (f: Subscriber<T[]>) => this.listStore.subscribe(f)
+
+  derived = <U>(f: (v: T[]) => U) => this.listStore.derived<U>(f)
+
+  throttle = (t: number) => this.listStore.throttle(t)
+
+  key = (k: string) => new Key(this.mapStore, this.pk, k)
+
+  set = (xs: T[]) => {
+    const m = new Map()
+
+    for (const x of xs) {
+      if (!x) {
+        console.error("Empty value passed to collection store")
+      } else if (!x[this.pk]) {
+        console.error(`Value with empty ${this.pk} passed to collection store`, x)
+      } else {
+        m.set(x[this.pk], x)
+      }
+    }
+
+    this.mapStore.set(m)
+  }
+
+  update = (f: (v: T[]) => T[]) => this.set(f(this.get()))
+
+  updateAsync = async (f: (v: T[]) => Promise<T[]>) => this.set(await f(this.get()))
+
+  reject = (f: (v: T) => boolean) => this.update((xs: T[]) => xs.filter(x => !f(x)))
+
+  filter = (f: (v: T) => boolean) => this.update((xs: T[]) => xs.filter(f))
+
+  map = (f: (v: T) => T) => this.update((xs: T[]) => xs.map(f))
+}
+
+export class DerivedCollection<T extends R> implements Readable<T[]> {
+  readonly listStore: Derived<T[]>
+  readonly mapStore: Readable<M<T>>
+
+  constructor(
+    readonly pk: string,
+    stores: Derivable,
+    getValue: (values: any) => T[],
+    t = 0,
+  ) {
+    this.listStore = new Derived(stores, getValue, t)
+    this.mapStore = new Derived(this.listStore, xs => new Map(xs.map((x: T) => [x[pk], x])))
+  }
+
+  get = () => this.listStore.get()
+
+  getMap = () => this.mapStore.get()
+
+  subscribe = (f: Subscriber<T[]>) => this.listStore.subscribe(f)
+
+  derived = <U>(f: (v: T[]) => U) => this.listStore.derived<U>(f)
+
+  throttle = (t: number) => this.listStore.throttle(t)
+
+  key = (k: string) => new DerivedKey(this.mapStore, this.pk, k)
+}
+
+export const writable = <T>(v: T) => new Writable(v)
+
+export const derived = <T>(stores: Derivable, getValue: (values: any) => T) =>
+  new Derived(stores, getValue)
+
+export const readable = <T>(v: T) => derived(new Writable(v), identity) as Readable<T>
+
+export const derivedCollection = <T extends R>(
+  pk: string,
+  stores: Derivable,
+  getValue: (values: any) => T[],
+) => new DerivedCollection(pk, stores, getValue)
+
+export const key = <T extends R>(base: Writable<M<T>>, pk: string, key: string) =>
+  new Key<T>(base, pk, key)
+
+export const collection = <T extends R>(pk: string) => new Collection<T>(pk)
diff --git a/packages/lib/Tools.ts b/packages/lib/Tools.ts
index fcff182..7dee934 100644
--- a/packages/lib/Tools.ts
+++ b/packages/lib/Tools.ts
@@ -28,6 +28,8 @@ export const toIterable = (x: any) => isIterable(x) ? x : [x]
 
 export const stripProtocol = (url: string) => url.replace(/.*:\/\//, "")
 
+export const ensurePlural = <T>(x: T | T[]) => (x instanceof Array ? x : [x])
+
 export const groupBy = <T>(f: (x: T) => string, xs: T[]) => {
   const r: Record<string, T[]> = {}
 
diff --git a/packages/lib/index.ts b/packages/lib/index.ts
index 4e5566a..9f0a840 100644
--- a/packages/lib/index.ts
+++ b/packages/lib/index.ts
@@ -3,6 +3,7 @@ export * from './Deferred'
 export * from './Emitter'
 export * from './Fluent'
 export * from './LRUCache'
-export * from './Worker'
+export * from './Store'
 export * from './Tools'
+export * from './Worker'
 export {default as normalizeUrl} from './normalize-url'
diff --git a/packages/lib/package.json b/packages/lib/package.json
index 66abdd2..c6e8ef5 100644
--- a/packages/lib/package.json
+++ b/packages/lib/package.json
@@ -27,11 +27,13 @@
   },
   "devDependencies": {
     "@types/events": "^3.0.3",
+    "@types/throttle-debounce": "^5.0.2",
     "gts": "^5.0.1",
     "tsc-multi": "^1.1.0",
     "typescript": "~5.1.6"
   },
   "dependencies": {
-    "@scure/base": "^1.1.6"
+    "@scure/base": "^1.1.6",
+    "throttle-debounce": "^5.0.0"
   }
 }
diff --git a/packages/util/Events.ts b/packages/util/Events.ts
index 6d41438..f736eee 100644
--- a/packages/util/Events.ts
+++ b/packages/util/Events.ts
@@ -68,4 +68,3 @@ export const isChildOf = (child: EventTemplate, parent: Rumor) => {
 
   return getIdAndAddress(parent).some(x => parentIds.includes(x))
 }
-