diff --git a/node/hypergraph/inmem/hypergraph_crdt.go b/node/hypergraph/inmem/hypergraph_crdt.go
new file mode 100644
index 0000000..d476cbd
--- /dev/null
+++ b/node/hypergraph/inmem/hypergraph_crdt.go
@@ -0,0 +1,242 @@
+package inmem
+
+import "errors"
+
+var ErrInvalidLocation error = errors.New("invalid location")
+var ErrMissingExtrinsics error = errors.New("missing extrinsics")
+var ErrIsExtrinsic error = errors.New("is extrinsic")
+
+type HypergraphCRDT struct {
+	locations map[Location]struct{}
+
+	vertexAdds       map[Location]*IdSet
+	vertexRemoves    map[Location]*IdSet
+	hyperedgeAdds    map[Location]*IdSet
+	hyperedgeRemoves map[Location]*IdSet
+}
+
+func NewHypergraphCRDT(locations []Location) *HypergraphCRDT {
+	hypergraph := &HypergraphCRDT{
+		locations:        make(map[Location]struct{}),
+		vertexAdds:       make(map[Location]*IdSet),
+		vertexRemoves:    make(map[Location]*IdSet),
+		hyperedgeAdds:    make(map[Location]*IdSet),
+		hyperedgeRemoves: make(map[Location]*IdSet),
+	}
+
+	for _, l := range locations {
+		hypergraph.locations[l] = struct{}{}
+		hypergraph.vertexAdds[l] = NewIdSet("vertex")
+		hypergraph.vertexRemoves[l] = NewIdSet("vertex")
+		hypergraph.hyperedgeAdds[l] = NewIdSet("hyperedge")
+		hypergraph.hyperedgeRemoves[l] = NewIdSet("hyperedge")
+	}
+
+	return hypergraph
+}
+
+func (hg *HypergraphCRDT) AddAtom(a Atom) error {
+	switch v := a.(type) {
+	case *Vertex:
+		hg.AddVertex(v)
+		return nil
+	case *Hyperedge:
+		return hg.AddHyperedge(v)
+	}
+
+	return nil
+}
+
+func (hg *HypergraphCRDT) AddVertex(v *Vertex) {
+	shardMap := ShardVertex(v)
+	for location, vertices := range shardMap {
+		for _, vertex := range vertices.VertexSet.atoms {
+			if vert, ok := vertex.(*Vertex); ok {
+				hg.vertexAdds[location].Add(vert)
+			}
+		}
+	}
+}
+
+func (hg *HypergraphCRDT) AddVertexSet(vertices *IdSet) error {
+	if vertices.atomType != "vertex" {
+		return ErrInvalidAtomType
+	}
+
+	shardMap := ShardAtomSet(vertices.atoms)
+	for location, vertices := range shardMap {
+		for _, vertex := range vertices.VertexSet.atoms {
+			if vert, ok := vertex.(*Vertex); ok {
+				hg.vertexAdds[location].Add(vert)
+			}
+		}
+	}
+
+	return nil
+}
+
+func (hg *HypergraphCRDT) AddHyperedge(h *Hyperedge) error {
+	if hg.LookupAtomSet(h.extrinsics) {
+		shardMap := ShardHyperedge(h)
+
+		for location, set := range shardMap {
+			for _, hyperedge := range set.HyperedgeSet.atoms {
+				if he, ok := hyperedge.(*Hyperedge); ok {
+					hg.hyperedgeAdds[location].Add(he)
+				}
+			}
+			for _, vertex := range set.VertexSet.atoms {
+				if v, ok := vertex.(*Vertex); ok {
+					hg.hyperedgeAdds[location].Add(v)
+				}
+			}
+		}
+
+		return nil
+	} else {
+		return ErrMissingExtrinsics
+	}
+}
+
+func (hg *HypergraphCRDT) RemoveAtom(a Atom) error {
+	switch v := a.(type) {
+	case *Vertex:
+		return hg.RemoveVertex(v)
+	case *Hyperedge:
+		return hg.RemoveHyperedge(v)
+	}
+
+	return nil
+}
+
+func (hg *HypergraphCRDT) RemoveVertex(v *Vertex) error {
+	if hg.LookupVertex(v) {
+		for l, hyperedgeAdds := range hg.hyperedgeAdds {
+			for _, hyperedge := range hyperedgeAdds.atoms {
+				he, ok := hyperedge.(*Hyperedge)
+				if !ok {
+					continue
+				}
+				if !hg.hyperedgeRemoves[l].Has(he) {
+					if _, ok := he.extrinsics[v.GetID()]; ok {
+						return ErrIsExtrinsic
+					}
+				}
+			}
+		}
+
+		hg.vertexRemoves[v.location].Add(v)
+	}
+
+	return nil
+}
+
+func (hg *HypergraphCRDT) RemoveHyperedge(h *Hyperedge) error {
+	if hg.LookupAtom(h) {
+		for l, hyperedgeAdds := range hg.hyperedgeAdds {
+			for _, hyperedge := range hyperedgeAdds.atoms {
+				he, ok := hyperedge.(*Hyperedge)
+				if !ok || hg.hyperedgeRemoves[l].Has(he) {
+					continue
+				}
+				if _, ok := he.extrinsics[h.GetID()]; ok {
+					return ErrIsExtrinsic
+				}
+			}
+		}
+
+		hg.hyperedgeRemoves[h.location].Add(h)
+	}
+
+	return nil
+}
+
+func (hg *HypergraphCRDT) LookupAtom(a Atom) bool {
+	if _, ok := hg.locations[a.GetLocation()]; !ok {
+		return false
+	}
+
+	switch v := a.(type) {
+	case *Vertex:
+		return hg.LookupVertex(v)
+	case *Hyperedge:
+		return hg.LookupHyperedge(v)
+	default:
+		return false
+	}
+}
+
+// LookupAtomSet checks all atoms in an IdSet to see if they all can be looked
+// up successfully.
+func (hg *HypergraphCRDT) LookupAtomSet(atomSet map[string]Atom) bool {
+	for _, atom := range atomSet {
+		if !hg.LookupAtom(atom) {
+			return false
+		}
+	}
+	return true
+}
+
+// LookupVertex checks if a vertex is added and not removed in the current
+// location.
+func (hg *HypergraphCRDT) LookupVertex(v *Vertex) bool {
+	location := v.GetLocation()
+	return hg.vertexAdds[location].Has(v) && !hg.vertexRemoves[location].Has(v)
+}
+
+// LookupHyperedge checks if a hyperedge and its extrinsics can be looked up.
+func (hg *HypergraphCRDT) LookupHyperedge(h *Hyperedge) bool {
+	return hg.LookupAtomSet(h.extrinsics) &&
+		hg.hyperedgeAdds[h.GetLocation()].Has(h) &&
+		!hg.hyperedgeRemoves[h.GetLocation()].Has(h)
+}
+
+// Within checks if atom `a` is within hyperedge `h` directly or transitively.
+func (hg *HypergraphCRDT) Within(a, h Atom) bool {
+	switch ha := h.(type) {
+	case *Hyperedge:
+		_, ok := ha.extrinsics[a.GetID()]
+		if ok || a.GetID() == h.GetID() {
+			return true
+		}
+		for _, extrinsic := range ha.extrinsics {
+			if he, ok := extrinsic.(*Hyperedge); ok {
+				for _, hyperExtrinsic := range he.extrinsics {
+					if hyperHe, ok := hyperExtrinsic.(*Hyperedge); ok {
+						if hg.LookupHyperedge(hyperHe) {
+							if _, ok := hyperHe.extrinsics[a.GetID()]; ok &&
+								hg.Within(hyperHe, h) {
+								return true
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+	return false
+}
+
+// GetReconciledVertexSet computes the set of vertices that have been added but
+// not removed for a location.
+func (hg *HypergraphCRDT) GetReconciledVertexSet(l Location) *IdSet {
+	vertices := NewIdSet("vertex")
+	for _, v := range hg.vertexAdds[l].atoms {
+		if !hg.vertexRemoves[l].Has(v) {
+			vertices.Add(v)
+		}
+	}
+	return vertices
+}
+
+// GetReconciledHyperedgeSet computes the set of hyperedges that have been added
+// but not removed for a location.
+func (hg *HypergraphCRDT) GetReconciledHyperedgeSet(l Location) *IdSet {
+	hyperedges := NewIdSet("hyperedge")
+	for _, h := range hg.hyperedgeAdds[l].atoms {
+		if !hg.hyperedgeRemoves[l].Has(h) {
+			hyperedges.Add(h)
+		}
+	}
+	return hyperedges
+}
diff --git a/node/hypergraph/inmem/hypergraph_test.go b/node/hypergraph/inmem/hypergraph_test.go
new file mode 100644
index 0000000..16a2327
--- /dev/null
+++ b/node/hypergraph/inmem/hypergraph_test.go
@@ -0,0 +1,75 @@
+package inmem_test
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	hypergraph "source.quilibrium.com/quilibrium/monorepo/node/hypergraph/inmem"
+)
+
+func TestIdSet(t *testing.T) {
+	v := hypergraph.NewVertex("1", "here")
+	h := hypergraph.NewHyperedge("2", "here", make(map[string]hypergraph.Atom))
+
+	vset := hypergraph.NewIdSet("vertex")
+	hset := hypergraph.NewIdSet("hyperedge")
+	assert.NoError(t, vset.Add(v))
+	assert.NoError(t, hset.Add(h))
+
+	assert.True(t, vset.Has(v))
+	assert.True(t, hset.Has(h))
+
+	vset.Delete(v)
+	assert.False(t, hset.Has(v))
+}
+
+func TestCRDT(t *testing.T) {
+	loc1 := hypergraph.Location("here1")
+	loc2 := hypergraph.Location("here2")
+	hg := hypergraph.NewHypergraphCRDT([]hypergraph.Location{loc1, loc2})
+
+	v1 := hypergraph.NewVertex("1", loc1)
+	v2 := hypergraph.NewVertex("2", loc2)
+	h1 := hypergraph.NewHyperedge("h1", loc1, make(map[string]hypergraph.Atom))
+
+	hg.AddVertex(v1)
+	hg.AddVertex(v2)
+	hg.AddHyperedge(h1)
+	h2vs := map[string]hypergraph.Atom{}
+	h2vs["1"] = v1
+	h2vs["2"] = v2
+	h2 := hypergraph.NewHyperedge("h2", loc2, h2vs)
+	hg.AddHyperedge(h2)
+
+	h3vs := map[string]hypergraph.Atom{}
+	h3vs["h2"] = h2
+	h3 := hypergraph.NewHyperedge("h3", loc1, h3vs)
+	hg.AddHyperedge(h3)
+
+	assert.NotNil(t, hg.LookupVertex(v1))
+	assert.NotNil(t, hg.LookupVertex(v2))
+	assert.NotNil(t, hg.LookupHyperedge(h1))
+	assert.NotNil(t, hg.LookupHyperedge(h2))
+	assert.NotNil(t, hg.LookupHyperedge(h3))
+
+	assert.True(t, hg.GetReconciledVertexSet(v1.GetLocation()).Has(v1))
+	assert.False(t, hg.GetReconciledVertexSet(v1.GetLocation()).Has(v2))
+	assert.True(t, hg.GetReconciledVertexSet(v2.GetLocation()).Has(v2))
+	assert.True(t, hg.GetReconciledHyperedgeSet(v1.GetLocation()).Has(h1))
+	assert.False(t, hg.GetReconciledHyperedgeSet(h1.GetLocation()).Has(h2))
+	assert.True(t, hg.GetReconciledHyperedgeSet(h2.GetLocation()).Has(h2))
+	assert.True(t, hg.GetReconciledHyperedgeSet(h3.GetLocation()).Has(h3))
+
+	assert.Error(t, hg.RemoveHyperedge(h2))
+	assert.True(t, hg.GetReconciledHyperedgeSet(h2.GetLocation()).Has(h2))
+	assert.NoError(t, hg.RemoveHyperedge(h3))
+	assert.False(t, hg.GetReconciledHyperedgeSet(h3.GetLocation()).Has(h3))
+	assert.Error(t, hg.RemoveVertex(v1))
+	assert.True(t, hg.GetReconciledVertexSet(v1.GetLocation()).Has(v1))
+	assert.NoError(t, hg.RemoveHyperedge(h2))
+	assert.False(t, hg.GetReconciledHyperedgeSet(h2.GetLocation()).Has(h2))
+	assert.NoError(t, hg.RemoveVertex(v1))
+	assert.False(t, hg.GetReconciledVertexSet(v1.GetLocation()).Has(v1))
+	assert.NoError(t, hg.RemoveVertex(v2))
+	assert.False(t, hg.GetReconciledVertexSet(v2.GetLocation()).Has(v2))
+}
diff --git a/node/hypergraph/inmem/shard.go b/node/hypergraph/inmem/shard.go
new file mode 100644
index 0000000..df88ff5
--- /dev/null
+++ b/node/hypergraph/inmem/shard.go
@@ -0,0 +1,89 @@
+package inmem
+
+func InShard(a Atom, l Location) bool {
+	return a.GetLocation() == l
+}
+
+type ShardSet struct {
+	VertexSet    *IdSet
+	HyperedgeSet *IdSet
+}
+
+func ShardAtom(a Atom) map[Location]*ShardSet {
+	switch atom := a.(type) {
+	case *Vertex:
+		return ShardVertex(atom)
+	case *Hyperedge:
+		return ShardHyperedge(atom)
+	default:
+		return nil
+	}
+}
+
+func ShardAtomSet(atomSet map[string]Atom) map[Location]*ShardSet {
+	result := make(map[Location]*ShardSet)
+	for _, a := range atomSet {
+		result[a.GetLocation()] = &ShardSet{
+			VertexSet:    NewIdSet("vertex"),
+			HyperedgeSet: NewIdSet("hyperedge"),
+		}
+	}
+
+	for _, atom := range atomSet {
+		shard := ShardAtom(atom)
+		for location, locationShard := range shard {
+			for _, locationAtom := range locationShard.VertexSet.atoms {
+				if _, ok := result[location]; !ok {
+					result[location] = &ShardSet{
+						VertexSet:    NewIdSet("vertex"),
+						HyperedgeSet: NewIdSet("hyperedge"),
+					}
+				}
+				result[location].VertexSet.Add(locationAtom)
+			}
+			for _, locationAtom := range locationShard.HyperedgeSet.atoms {
+				if _, ok := result[location]; !ok {
+					result[location] = &ShardSet{
+						VertexSet:    NewIdSet("vertex"),
+						HyperedgeSet: NewIdSet("hyperedge"),
+					}
+				}
+				result[location].HyperedgeSet.Add(locationAtom)
+			}
+		}
+	}
+	return result
+}
+
+func ShardVertex(v *Vertex) map[Location]*ShardSet {
+	result := make(map[Location]*ShardSet)
+	if _, ok := result[v.location]; !ok {
+		result[v.location] = &ShardSet{
+			VertexSet:    NewIdSet("vertex"),
+			HyperedgeSet: NewIdSet("hyperedge"),
+		}
+	}
+	result[v.location].VertexSet.Add(v)
+	return result
+}
+
+// ShardHyperedge shards a hyperedge and its extrinsics across locations.
+func ShardHyperedge(h *Hyperedge) map[Location]*ShardSet {
+	extrinsicShardSet := ShardAtomSet(h.extrinsics)
+	result := make(map[Location]*ShardSet)
+
+	for l, s := range extrinsicShardSet {
+		result[l] = s
+	}
+
+	if _, ok := result[h.location]; !ok {
+		result[h.location] = &ShardSet{
+			VertexSet:    NewIdSet("vertex"),
+			HyperedgeSet: NewIdSet("hyperedge"),
+		}
+	}
+
+	result[h.location].HyperedgeSet.Add(h)
+
+	return result
+}
diff --git a/node/hypergraph/inmem/types.go b/node/hypergraph/inmem/types.go
new file mode 100644
index 0000000..cc5ac79
--- /dev/null
+++ b/node/hypergraph/inmem/types.go
@@ -0,0 +1,133 @@
+package inmem
+
+import "errors"
+
+type AtomType string
+type Location string
+
+var ErrInvalidAtomType error = errors.New("invalid atom type for set")
+
+type Vertex struct {
+	id       string
+	location Location
+}
+
+type Hyperedge struct {
+	id         string
+	location   Location
+	extrinsics map[string]Atom
+}
+
+type Atom interface {
+	GetID() string
+	GetAtomType() AtomType
+	GetLocation() Location
+}
+
+var _v Atom = (*Vertex)(nil)
+var _h Atom = (*Hyperedge)(nil)
+
+func NewVertex(id string, location Location) *Vertex {
+	return &Vertex{
+		id,
+		location,
+	}
+}
+
+func NewHyperedge(
+	id string,
+	location Location,
+	extrinsics map[string]Atom,
+) *Hyperedge {
+	return &Hyperedge{
+		id,
+		location,
+		extrinsics,
+	}
+}
+
+func (v *Vertex) GetID() string {
+	return v.id
+}
+
+func (h *Hyperedge) GetID() string {
+	return h.id
+}
+
+func (v *Vertex) GetAtomType() AtomType {
+	return "vertex"
+}
+
+func (h *Hyperedge) GetAtomType() AtomType {
+	return "hyperedge"
+}
+
+func (v *Vertex) GetLocation() Location {
+	return v.location
+}
+
+func (h *Hyperedge) GetLocation() Location {
+	return h.location
+}
+
+type IdSet struct {
+	atomType AtomType
+	atoms    map[string]Atom
+}
+
+func NewIdSet(atomType AtomType) *IdSet {
+	return &IdSet{atomType: atomType, atoms: make(map[string]Atom)}
+}
+
+// Add adds an atom to the IdSet if it's not already present.
+func (set *IdSet) Add(atom Atom) error {
+	switch a := atom.(type) {
+	case *Vertex:
+		if set.atomType != "vertex" {
+			return ErrInvalidAtomType
+		}
+		if _, exists := set.atoms[a.GetID()]; !exists {
+			set.atoms[a.GetID()] = a
+		}
+	case *Hyperedge:
+		if set.atomType != "hyperedge" {
+			return ErrInvalidAtomType
+		}
+		if _, exists := set.atoms[a.GetID()]; !exists {
+			set.atoms[a.GetID()] = a
+		}
+	}
+
+	return nil
+}
+
+// Delete removes an atom from the IdSet and returns true if the atom was
+// present.
+func (set *IdSet) Delete(atom Atom) bool {
+	switch a := atom.(type) {
+	case *Vertex:
+		if _, exists := set.atoms[a.GetID()]; exists {
+			delete(set.atoms, a.GetID())
+			return true
+		}
+	case *Hyperedge:
+		if _, exists := set.atoms[a.GetID()]; exists {
+			delete(set.atoms, a.GetID())
+			return true
+		}
+	}
+	return false
+}
+
+// Has checks if an atom is in the IdSet.
+func (set *IdSet) Has(atom Atom) bool {
+	switch a := atom.(type) {
+	case *Vertex:
+		_, exists := set.atoms[a.GetID()]
+		return exists
+	case *Hyperedge:
+		_, exists := set.atoms[a.GetID()]
+		return exists
+	}
+	return false
+}