diff --git a/backends/factos_cf_workers/src/factos/factos_cf_workers.gleam b/backends/factos_cf_workers/src/factos/factos_cf_workers.gleam
index 85ea1e0..99ccb43 100644
--- a/backends/factos_cf_workers/src/factos/factos_cf_workers.gleam
+++ b/backends/factos_cf_workers/src/factos/factos_cf_workers.gleam
@@ -31,6 +31,7 @@ pub type Proposed(event) {
     id: String,
     event: event,
     type_: factos.EventType,
+    version: Int,
     tags: List(factos.Tag),
     metadata: factos.Metadata,
     data: String,
@@ -45,6 +46,7 @@ pub type StoredEvent {
     stream: String,
     revision: Int,
     type_: factos.EventType,
+    version: Int,
     tags: List(factos.Tag),
     metadata: factos.Metadata,
     data: String,
@@ -102,6 +104,7 @@ pub fn migrate(database: d1.Database) -> Promise(Result(Nil, Error(_, _))) {
       stream text not null,
       revision integer not null,
       type text not null,
+      version integer not null,
       tags text not null,
       metadata text not null,
       data text not null,
@@ -329,7 +332,7 @@ fn read_matching_events(
 ) {
   d1.prepare(
     database,
-    "select position, id, stream, revision, type, tags, metadata, data from factos_events order by position",
+    "select position, id, stream, revision, type, version, tags, metadata, data from factos_events order by position",
   )
   |> d1.raw
   |> promise.map(fn(result) {
@@ -348,7 +351,7 @@ fn read_stream_events(
 ) {
   d1.prepare(
     database,
-    "select position, id, stream, revision, type, tags, metadata, data from factos_events where stream = ? order by revision",
+    "select position, id, stream, revision, type, version, tags, metadata, data from factos_events where stream = ? order by revision",
   )
   |> d1.bind([stream_name])
   |> d1.raw
@@ -395,8 +398,8 @@ fn decode_row(
   use decoded <- result.try(
     decode_event(stored) |> result.map_error(DecodeError),
   )
-  let factos.Decoded(event, type_, tags, metadata) = decoded
-  let StoredEvent(position, id, stream, revision, _, _, _, _) = stored
+  let factos.Decoded(event, type_, version, tags, metadata) = decoded
+  let StoredEvent(position, id, stream, revision, _, _, _, _, _) = stored
 
   Ok(factos.Recorded(
     id: id,
@@ -404,6 +407,7 @@ fn decode_row(
     revision: revision,
     position: factos.SequencePosition(position),
     type_: type_,
+    version: version,
     tags: tags,
     metadata: metadata,
     event: event,
@@ -418,9 +422,10 @@ fn decode_stored_event(
   use stream <- result.try(decode_string_field(row, 2))
   use revision <- result.try(decode_int_field(row, 3))
   use type_name <- result.try(decode_string_field(row, 4))
-  use tags <- result.try(decode_string_field(row, 5))
-  use metadata <- result.try(decode_string_field(row, 6))
-  use data <- result.try(decode_string_field(row, 7))
+  use version <- result.try(decode_int_field(row, 5))
+  use tags <- result.try(decode_string_field(row, 6))
+  use metadata <- result.try(decode_string_field(row, 7))
+  use data <- result.try(decode_string_field(row, 8))
 
   Ok(StoredEvent(
     position: position,
@@ -428,6 +433,7 @@ fn decode_stored_event(
     stream: stream,
     revision: revision,
     type_: factos.event_type(type_name),
+    version: version,
     tags: tags_from_text(tags),
     metadata: metadata_from_text(metadata),
     data: data,
@@ -483,7 +489,7 @@ fn append_sql(
     })
 
   let sql =
-    "insert into factos_events (id, stream, revision, type, tags, metadata, data) "
+    "insert into factos_events (id, stream, revision, type, version, tags, metadata, data) "
     <> string.join(list.map(rows, fn(row) { row.0 }), with: " union all ")
     <> " returning position, revision"
 
@@ -499,13 +505,14 @@ fn append_select_sql(
   index: Int,
 ) -> #(String, List(String)) {
   let EventCodec(encode, _) = codec
-  let Proposed(id, _, type_, tags, metadata, data) = encode(event)
+  let Proposed(id, _, type_, version, tags, metadata, data) = encode(event)
   let base_values = [
     id,
     stream_name,
     stream_name,
     int.to_string(index + 1),
     factos.event_type_name(type_),
+    int.to_string(version),
     tags_to_text(tags),
     metadata_to_text(metadata),
     data,
@@ -513,7 +520,7 @@ fn append_select_sql(
 
   let #(condition, condition_values) = append_condition_sql(stream_name, mode)
   #(
-    "select ?, ?, (select coalesce(max(revision), -1) from factos_events where stream = ?) + cast(? as integer), ?, ?, ?, ? where "
+    "select ?, ?, (select coalesce(max(revision), -1) from factos_events where stream = ?) + cast(? as integer), ?, cast(? as integer), ?, ?, ? where "
       <> condition,
     list.append(base_values, condition_values),
   )
diff --git a/backends/factos_cf_workers/test/factos_cf_workers_test.gleam b/backends/factos_cf_workers/test/factos_cf_workers_test.gleam
index 9611b14..32b2301 100644
--- a/backends/factos_cf_workers/test/factos_cf_workers_test.gleam
+++ b/backends/factos_cf_workers/test/factos_cf_workers_test.gleam
@@ -286,6 +286,7 @@ fn encode(event: Event) -> backend.Proposed(Event) {
         id: "event-" <> name,
         event: event,
         type_: factos.event_type("reserved"),
+        version: 1,
         tags: [factos.tag("name:" <> name)],
         metadata: factos.empty_metadata(),
         data: name,
@@ -301,6 +302,7 @@ fn decode(
       Ok(factos.Decoded(
         event: Reserved(stored.data),
         type_: stored.type_,
+        version: stored.version,
         tags: stored.tags,
         metadata: stored.metadata,
       ))
diff --git a/backends/factos_kurrentdb_erlang/src/factos/factos_kurrentdb_erlang.gleam b/backends/factos_kurrentdb_erlang/src/factos/factos_kurrentdb_erlang.gleam
index 1b19c46..3e636af 100644
--- a/backends/factos_kurrentdb_erlang/src/factos/factos_kurrentdb_erlang.gleam
+++ b/backends/factos_kurrentdb_erlang/src/factos/factos_kurrentdb_erlang.gleam
@@ -33,6 +33,7 @@ pub type Proposed(event) {
   Proposed(
     event: event,
     type_: factos.EventType,
+    version: Int,
     tags: List(factos.Tag),
     metadata: factos.Metadata,
     message: append_to_stream.Event,
@@ -541,13 +542,14 @@ fn decode_recorded(
     |> result.map_error(DecodeError),
   )
 
-  let factos.Decoded(event, type_, tags, metadata) = decoded
+  let factos.Decoded(event, type_, version, tags, metadata) = decoded
   Ok(factos.Recorded(
     id: uuid.to_string(recorded_event.id),
     stream: recorded_event.stream,
     revision: recorded_event.revision,
     position: factos.SequencePosition(recorded_event.commit_position),
     type_: type_,
+    version: version,
     tags: tags,
     metadata: metadata,
     event: event,
diff --git a/backends/factos_kurrentdb_erlang/test/factos_kurrentdb_erlang_test.gleam b/backends/factos_kurrentdb_erlang/test/factos_kurrentdb_erlang_test.gleam
index b0de283..26cd640 100644
--- a/backends/factos_kurrentdb_erlang/test/factos_kurrentdb_erlang_test.gleam
+++ b/backends/factos_kurrentdb_erlang/test/factos_kurrentdb_erlang_test.gleam
@@ -205,6 +205,7 @@ fn encode_counter_event(
       factos_kurrentdb_erlang.Proposed(
         event: event,
         type_: factos.event_type(event_type),
+        version: 1,
         tags: [factos.tag("counter:load")],
         metadata: factos.empty_metadata(),
         message: append_to_stream.binary_event(
@@ -233,6 +234,7 @@ fn decode_counter_event(
       Ok(factos.Decoded(
         event: Incremented(value),
         type_: factos.event_type(event_type),
+        version: 1,
         tags: [factos.tag("counter:load")],
         metadata: factos.empty_metadata(),
       ))
diff --git a/backends/factos_pog/src/factos/factos_pog.gleam b/backends/factos_pog/src/factos/factos_pog.gleam
index e3c357a..ead590c 100644
--- a/backends/factos_pog/src/factos/factos_pog.gleam
+++ b/backends/factos_pog/src/factos/factos_pog.gleam
@@ -31,6 +31,7 @@ pub type Proposed(event) {
     id: String,
     event: event,
     type_: factos.EventType,
+    version: Int,
     tags: List(factos.Tag),
     metadata: factos.Metadata,
     data: BitArray,
@@ -48,6 +49,7 @@ pub type StoredEvent {
     stream: String,
     revision: Int,
     type_: factos.EventType,
+    version: Int,
     tags: List(factos.Tag),
     metadata: factos.Metadata,
     data: BitArray,
@@ -108,6 +110,7 @@ pub fn migrate(connection: pog.Connection) -> Result(Nil, Error(_, _)) {
       stream text not null,
       revision integer not null,
       type text not null,
+      version integer not null,
       tags text not null,
       metadata text not null,
       data bytea not null,
@@ -383,12 +386,12 @@ fn insert_events(
     [] -> Ok(Append(current_revision: revision - 1, position: position))
     [event, ..rest] -> {
       let EventCodec(encode, _) = codec
-      let Proposed(id, _, type_, tags, metadata, data) = encode(event)
+      let Proposed(id, _, type_, version, tags, metadata, data) = encode(event)
       use returned <- result.try(
         pog.query(
           "
-          insert into factos_events (id, stream, revision, type, tags, metadata, data)
-          values ($1, $2, $3, $4, $5, $6, $7)
+          insert into factos_events (id, stream, revision, type, version, tags, metadata, data)
+          values ($1, $2, $3, $4, $5, $6, $7, $8)
           returning position
           ",
         )
@@ -396,6 +399,7 @@ fn insert_events(
         |> pog.parameter(pog.text(stream_name))
         |> pog.parameter(pog.int(revision))
         |> pog.parameter(pog.text(factos.event_type_name(type_)))
+        |> pog.parameter(pog.int(version))
         |> pog.parameter(pog.text(tags_to_text(tags)))
         |> pog.parameter(pog.text(metadata_to_text(metadata)))
         |> pog.parameter(pog.bytea(data))
@@ -426,7 +430,7 @@ fn read_matching_events(
 ) -> Result(List(factos.Recorded(event)), Error(domain_error, decode_error)) {
   use rows <- result.try(
     pog.query(
-      "select position, id, stream, revision, type, tags, metadata, data from factos_events order by position",
+      "select position, id, stream, revision, type, version, tags, metadata, data from factos_events order by position",
     )
     |> pog.returning(stored_event_decoder())
     |> pog.execute(on: connection)
@@ -444,7 +448,7 @@ fn read_stream_events(
 ) -> Result(List(factos.Recorded(event)), Error(domain_error, decode_error)) {
   use rows <- result.try(
     pog.query(
-      "select position, id, stream, revision, type, tags, metadata, data from factos_events where stream = $1 order by revision",
+      "select position, id, stream, revision, type, version, tags, metadata, data from factos_events where stream = $1 order by revision",
     )
     |> pog.parameter(pog.text(stream_name))
     |> pog.returning(stored_event_decoder())
@@ -475,8 +479,8 @@ fn decode_row(
 ) -> Result(factos.Recorded(event), Error(domain_error, decode_error)) {
   let EventCodec(_, decode_event) = codec
   use decoded <- result.try(decode_event(row) |> result.map_error(DecodeError))
-  let factos.Decoded(event, type_, tags, metadata) = decoded
-  let StoredEvent(position, id, stream, revision, _, _, _, _) = row
+  let factos.Decoded(event, type_, version, tags, metadata) = decoded
+  let StoredEvent(position, id, stream, revision, _, _, _, _, _) = row
 
   Ok(factos.Recorded(
     id: id,
@@ -484,6 +488,7 @@ fn decode_row(
     revision: revision,
     position: factos.SequencePosition(position),
     type_: type_,
+    version: version,
     tags: tags,
     metadata: metadata,
     event: event,
@@ -496,15 +501,17 @@ fn stored_event_decoder() -> decode.Decoder(StoredEvent) {
   use stream <- decode.field(2, decode.string)
   use revision <- decode.field(3, decode.int)
   use type_name <- decode.field(4, decode.string)
-  use tags <- decode.field(5, decode.string)
-  use metadata <- decode.field(6, decode.string)
-  use data <- decode.field(7, decode.bit_array)
+  use version <- decode.field(5, decode.int)
+  use tags <- decode.field(6, decode.string)
+  use metadata <- decode.field(7, decode.string)
+  use data <- decode.field(8, decode.bit_array)
   decode.success(StoredEvent(
     position: position,
     id: id,
     stream: stream,
     revision: revision,
     type_: factos.event_type(type_name),
+    version: version,
     tags: tags_from_text(tags),
     metadata: metadata_from_text(metadata),
     data: data,
@@ -575,6 +582,7 @@ fn matches_query_parts(
       revision: 0,
       position: factos.NoPosition,
       type_: type_,
+      version: 1,
       tags: tags,
       metadata: factos.empty_metadata(),
       event: Nil,
diff --git a/backends/factos_pog/test/factos_pog_test.gleam b/backends/factos_pog/test/factos_pog_test.gleam
index b07a811..bcf280c 100644
--- a/backends/factos_pog/test/factos_pog_test.gleam
+++ b/backends/factos_pog/test/factos_pog_test.gleam
@@ -199,6 +199,7 @@ fn encode(event: Event) -> factos_pog.Proposed(Event) {
     id: "event-" <> event.username,
     event: event,
     type_: factos.event_type("UserRegistered"),
+    version: 1,
     tags: [factos.tag("username:" <> event.username)],
     metadata: factos.empty_metadata(),
     data: bit_array.from_string(event.username),
@@ -217,6 +218,7 @@ fn decode(
       Ok(factos.Decoded(
         event: UserRegistered(username),
         type_: stored.type_,
+        version: stored.version,
         tags: stored.tags,
         metadata: stored.metadata,
       ))
@@ -307,6 +309,7 @@ fn encode_counter_event(
         id: "counter-event-" <> int.to_string(value),
         event: event,
         type_: factos.event_type("Incremented"),
+        version: 1,
         tags: [factos.tag("counter:load")],
         metadata: factos.empty_metadata(),
         data: bit_array.from_string(int.to_string(value)),
@@ -330,6 +333,7 @@ fn decode_counter_event(
       Ok(factos.Decoded(
         event: Incremented(value),
         type_: stored.type_,
+        version: stored.version,
         tags: stored.tags,
         metadata: stored.metadata,
       ))
diff --git a/backends/factos_sqlight/src/factos/factos_sqlight.gleam b/backends/factos_sqlight/src/factos/factos_sqlight.gleam
index 0ae97fb..b2c5f61 100644
--- a/backends/factos_sqlight/src/factos/factos_sqlight.gleam
+++ b/backends/factos_sqlight/src/factos/factos_sqlight.gleam
@@ -34,6 +34,7 @@ pub type Proposed(event) {
     id: String,
     event: event,
     type_: factos.EventType,
+    version: Int,
     tags: List(factos.Tag),
     metadata: factos.Metadata,
     data: BitArray,
@@ -52,6 +53,7 @@ pub type StoredEvent {
     stream: String,
     revision: Int,
     type_: factos.EventType,
+    version: Int,
     tags: List(factos.Tag),
     metadata: factos.Metadata,
     data: BitArray,
@@ -108,6 +110,7 @@ pub fn migrate(connection: sqlight.Connection) -> Result(Nil, Error(_, _)) {
       stream text not null,
       revision integer not null,
       type text not null,
+      version integer not null,
       tags text not null,
       metadata text not null default '',
       data blob not null,
@@ -373,12 +376,12 @@ fn insert_events(
     [] -> Ok(Append(current_revision: revision - 1, position: position))
     [event, ..rest] -> {
       let EventCodec(encode, _) = codec
-      let Proposed(id, _, type_, tags, metadata, data) = encode(event)
+      let Proposed(id, _, type_, version, tags, metadata, data) = encode(event)
       use positions <- result.try(
         sqlight.query(
           "
-          insert into factos_events (id, stream, revision, type, tags, metadata, data)
-          values (?, ?, ?, ?, ?, ?, ?)
+          insert into factos_events (id, stream, revision, type, version, tags, metadata, data)
+          values (?, ?, ?, ?, ?, ?, ?, ?)
           returning position
           ",
           on: connection,
@@ -387,6 +390,7 @@ fn insert_events(
             sqlight.text(stream_name),
             sqlight.int(revision),
             sqlight.text(factos.event_type_name(type_)),
+            sqlight.int(version),
             sqlight.text(tags_to_text(tags)),
             sqlight.text(metadata_to_text(metadata)),
             sqlight.blob(data),
@@ -418,7 +422,7 @@ fn read_matching_events(
 ) -> Result(List(factos.Recorded(event)), Error(domain_error, decode_error)) {
   use rows <- result.try(
     sqlight.query(
-      "select position, id, stream, revision, type, tags, metadata, data from factos_events order by position",
+      "select position, id, stream, revision, type, version, tags, metadata, data from factos_events order by position",
       on: connection,
       with: [],
       expecting: stored_event_decoder(),
@@ -436,7 +440,7 @@ fn read_stream_events(
 ) -> Result(List(factos.Recorded(event)), Error(domain_error, decode_error)) {
   use rows <- result.try(
     sqlight.query(
-      "select position, id, stream, revision, type, tags, metadata, data from factos_events where stream = ? order by revision",
+      "select position, id, stream, revision, type, version, tags, metadata, data from factos_events where stream = ? order by revision",
       on: connection,
       with: [sqlight.text(stream_name)],
       expecting: stored_event_decoder(),
@@ -466,8 +470,8 @@ fn decode_row(
 ) -> Result(factos.Recorded(event), Error(domain_error, decode_error)) {
   let EventCodec(_, decode_event) = codec
   use decoded <- result.try(decode_event(row) |> result.map_error(DecodeError))
-  let factos.Decoded(event, type_, tags, metadata) = decoded
-  let StoredEvent(position, id, stream, revision, _, _, _, _) = row
+  let factos.Decoded(event, type_, version, tags, metadata) = decoded
+  let StoredEvent(position, id, stream, revision, _, _, _, _, _) = row
 
   Ok(factos.Recorded(
     id: id,
@@ -475,6 +479,7 @@ fn decode_row(
     revision: revision,
     position: factos.SequencePosition(position),
     type_: type_,
+    version: version,
     tags: tags,
     metadata: metadata,
     event: event,
@@ -487,15 +492,17 @@ fn stored_event_decoder() -> decode.Decoder(StoredEvent) {
   use stream <- decode.field(2, decode.string)
   use revision <- decode.field(3, decode.int)
   use type_name <- decode.field(4, decode.string)
-  use tags <- decode.field(5, decode.string)
-  use metadata <- decode.field(6, decode.string)
-  use data <- decode.field(7, decode.bit_array)
+  use version <- decode.field(5, decode.int)
+  use tags <- decode.field(6, decode.string)
+  use metadata <- decode.field(7, decode.string)
+  use data <- decode.field(8, decode.bit_array)
   decode.success(StoredEvent(
     position: position,
     id: id,
     stream: stream,
     revision: revision,
     type_: factos.event_type(type_name),
+    version: version,
     tags: tags_from_text(tags),
     metadata: metadata_from_text(metadata),
     data: data,
@@ -567,6 +574,7 @@ fn matches_query_parts(
       revision: 0,
       position: factos.NoPosition,
       type_: type_,
+      version: 1,
       tags: tags,
       metadata: factos.empty_metadata(),
       event: Nil,
diff --git a/backends/factos_sqlight/test/factos_sqlight_test.gleam b/backends/factos_sqlight/test/factos_sqlight_test.gleam
index 3a9034d..2caa161 100644
--- a/backends/factos_sqlight/test/factos_sqlight_test.gleam
+++ b/backends/factos_sqlight/test/factos_sqlight_test.gleam
@@ -145,6 +145,7 @@ fn encode(event: Event) -> factos_sqlight.Proposed(Event) {
     id: "event-" <> event.username,
     event: event,
     type_: factos.event_type("UserRegistered"),
+    version: 1,
     tags: [factos.tag("username:" <> event.username)],
     metadata: factos.empty_metadata(),
     data: bit_array.from_string(event.username),
@@ -163,6 +164,7 @@ fn decode(
       Ok(factos.Decoded(
         event: UserRegistered(username),
         type_: stored.type_,
+        version: stored.version,
         tags: stored.tags,
         metadata: stored.metadata,
       ))
@@ -284,6 +286,7 @@ fn encode_counter_event(
         id: "counter-event-" <> int.to_string(value),
         event: event,
         type_: factos.event_type("Incremented"),
+        version: 1,
         tags: [factos.tag("counter:load")],
         metadata: factos.empty_metadata(),
         data: bit_array.from_string(int.to_string(value)),
@@ -307,6 +310,7 @@ fn decode_counter_event(
       Ok(factos.Decoded(
         event: Incremented(value),
         type_: stored.type_,
+        version: stored.version,
         tags: stored.tags,
         metadata: stored.metadata,
       ))
diff --git a/examples/orders_sqlight/src/order_workflow.gleam b/examples/orders_sqlight/src/order_workflow.gleam
index 35403e9..010776b 100644
--- a/examples/orders_sqlight/src/order_workflow.gleam
+++ b/examples/orders_sqlight/src/order_workflow.gleam
@@ -701,6 +701,7 @@ fn proposed(
     id: "example-" <> type_name <> "-" <> fields_to_payload(fields),
     event: event,
     type_: factos.event_type(type_name),
+    version: 1,
     tags: [factos.tag("restaurant"), ..tags],
     metadata: factos.empty_metadata(),
     data: bit_array.from_string(fields_to_payload(fields)),
@@ -721,6 +722,7 @@ fn decode_event(
   Ok(factos.Decoded(
     event: event,
     type_: stored.type_,
+    version: stored.version,
     tags: stored.tags,
     metadata: stored.metadata,
   ))
diff --git a/examples/tickets_pog/src/ticket_sale.gleam b/examples/tickets_pog/src/ticket_sale.gleam
index 1b139ad..87cf8ea 100644
--- a/examples/tickets_pog/src/ticket_sale.gleam
+++ b/examples/tickets_pog/src/ticket_sale.gleam
@@ -282,6 +282,7 @@ fn encode_event(event: Event) -> factos_pog.Proposed(Event) {
         id: "ticket-sold-" <> buyer,
         event: event,
         type_: factos.event_type("TicketSold"),
+        version: 1,
         tags: [factos.tag("event:" <> event_id)],
         metadata: factos.empty_metadata(),
         data: bit_array.from_string(buyer),
@@ -301,6 +302,7 @@ fn decode_event(
       Ok(factos.Decoded(
         event: TicketSold(buyer),
         type_: stored.type_,
+        version: stored.version,
         tags: stored.tags,
         metadata: stored.metadata,
       ))
diff --git a/src/factos.gleam b/src/factos.gleam
index e377ab2..121663a 100644
--- a/src/factos.gleam
+++ b/src/factos.gleam
@@ -137,7 +137,13 @@ pub type Decoded(event) {
   /// Backends use codecs supplied by the application. The decoded value includes
   /// the domain event plus the event type and tags that should participate in
   /// query matching, along with non-query event metadata.
-  Decoded(event: event, type_: EventType, tags: List(Tag), metadata: Metadata)
+  Decoded(
+    event: event,
+    type_: EventType,
+    version: Int,
+    tags: List(Tag),
+    metadata: Metadata,
+  )
 }
 
 pub type Recorded(event) {
@@ -152,6 +158,7 @@ pub type Recorded(event) {
     revision: Int,
     position: SequencePosition,
     type_: EventType,
+    version: Int,
     tags: List(Tag),
     metadata: Metadata,
     event: event,
diff --git a/test/factos_test.gleam b/test/factos_test.gleam
index 196ef57..f8cfcbe 100644
--- a/test/factos_test.gleam
+++ b/test/factos_test.gleam
@@ -238,6 +238,7 @@ fn recorded(
     revision: revision,
     position: factos.SequencePosition(revision),
     type_: type_,
+    version: 1,
     tags: tags,
     metadata: factos.empty_metadata(),
     event: event,