diff --git a/CHANGES.md b/CHANGES.md
index 0dee0de88f40f59e6215143558261250e5669d2d..85a0c753d20c41e7350309d99b8b93c4b85d5c21 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -46,6 +46,11 @@ be documented here either.
   containing the configuration for a custom network,
   or a URL from which such a file can be downloaded.
 
+- Some RPCs now send their response in chunked transfer encoding.
+  Additionally, the implementation allows for more concurrency internally: it
+  allows RPC requests to be treated even if a request is currently being
+  treated. This leads to some improved response times on some RPC requests.
+
 ## Client
 
 - Fixed the return code of errors in the client calls to be non-zero.
diff --git a/src/lib_protocol_environment/environment_V0.ml b/src/lib_protocol_environment/environment_V0.ml
index 225402a248e25d93b694ea64cbfbb956e2be78bc..0422700c62c2d29999788306f0fa7a0a2c00b9e8 100644
--- a/src/lib_protocol_environment/environment_V0.ml
+++ b/src/lib_protocol_environment/environment_V0.ml
@@ -433,6 +433,8 @@ struct
 
     let return x = Lwt.return (`Ok x)
 
+    let return_chunked x = Lwt.return (`OkChunk x)
+
     let return_stream x = Lwt.return (`OkStream x)
 
     let not_found = Lwt.return (`Not_found None)
@@ -448,7 +450,7 @@ struct
           handler p q i
           >>= function
           | `Ok o ->
-              RPC_answer.return o
+              RPC_answer.return_chunked o
           | `OkStream s ->
               RPC_answer.return_stream s
           | `Created s ->
diff --git a/src/lib_protocol_environment/environment_V1.ml b/src/lib_protocol_environment/environment_V1.ml
index 3db4d284e096b99d079bb07a65dea40d37dd7260..fd8d723c73438bb66e51dfa6f60ab6d4b33888cf 100644
--- a/src/lib_protocol_environment/environment_V1.ml
+++ b/src/lib_protocol_environment/environment_V1.ml
@@ -620,6 +620,8 @@ struct
 
     let return x = Lwt.return (`Ok x)
 
+    let return_chunked x = Lwt.return (`OkChunk x)
+
     let return_stream x = Lwt.return (`OkStream x)
 
     let not_found = Lwt.return (`Not_found None)
@@ -635,7 +637,7 @@ struct
           handler p q i
           >>= function
           | `Ok o ->
-              RPC_answer.return o
+              RPC_answer.return_chunked o
           | `OkStream s ->
               RPC_answer.return_stream s
           | `Created s ->
diff --git a/src/lib_protocol_environment/environment_V2.ml b/src/lib_protocol_environment/environment_V2.ml
index 927c87a95510ed1c1e6e151da2e1602f51753aac..128916cc132842d6bb28df95b60e91156cb9fb5d 100644
--- a/src/lib_protocol_environment/environment_V2.ml
+++ b/src/lib_protocol_environment/environment_V2.ml
@@ -633,6 +633,8 @@ struct
 
     let return x = Lwt.return (`Ok x)
 
+    let return_chunked x = Lwt.return (`OkChunk x)
+
     let return_stream x = Lwt.return (`OkStream x)
 
     let not_found = Lwt.return (`Not_found None)
@@ -648,7 +650,7 @@ struct
           handler p q i
           >>= function
           | `Ok o ->
-              RPC_answer.return o
+              RPC_answer.return_chunked o
           | `OkStream s ->
               RPC_answer.return_stream s
           | `Created s ->
diff --git a/src/lib_rpc/RPC_answer.ml b/src/lib_rpc/RPC_answer.ml
index 06b5044d93539cfab2fd502a3ef92188e0007472..9d1dc54078773045f0cdd7c117b48dcdb6072f34 100644
--- a/src/lib_rpc/RPC_answer.ml
+++ b/src/lib_rpc/RPC_answer.ml
@@ -26,6 +26,7 @@
 (** Return type for service handler *)
 type 'o t =
   [ `Ok of 'o (* 200 *)
+  | `OkChunk of 'o (* 200 *)
   | `OkStream of 'o stream (* 200 *)
   | `Created of string option (* 201 *)
   | `No_content (* 204 *)
@@ -43,6 +44,8 @@ and 'a stream = 'a Resto_directory.Answer.stream = {
 
 let return x = Lwt.return (`Ok x)
 
+let return_chunked x = Lwt.return (`OkChunk x)
+
 let return_unit = Lwt.return (`Ok ())
 
 let return_stream x = Lwt.return (`OkStream x)
diff --git a/src/lib_rpc/RPC_answer.mli b/src/lib_rpc/RPC_answer.mli
index b82e4289d8b8b804aafb413f0972fc667ffaeff8..c4c451adad69291ab0942e1cb91aa1ad87def4af 100644
--- a/src/lib_rpc/RPC_answer.mli
+++ b/src/lib_rpc/RPC_answer.mli
@@ -26,6 +26,7 @@
 (** Return type for service handler *)
 type 'o t =
   [ `Ok of 'o (* 200 *)
+  | `OkChunk of 'o (* 200 *)
   | `OkStream of 'o stream (* 200 *)
   | `Created of string option (* 201 *)
   | `No_content (* 204 *)
@@ -43,6 +44,8 @@ and 'a stream = 'a Resto_directory.Answer.stream = {
 
 val return : 'o -> 'o t Lwt.t
 
+val return_chunked : 'o -> 'o t Lwt.t
+
 val return_unit : unit t Lwt.t
 
 val return_stream : 'o stream -> 'o t Lwt.t
diff --git a/src/lib_rpc/RPC_directory.ml b/src/lib_rpc/RPC_directory.ml
index bba7b8611228653544d1cb184d463fbea629d3b5..38e060275cfa89fcb57ca415587eac8dba1a4d03 100644
--- a/src/lib_rpc/RPC_directory.ml
+++ b/src/lib_rpc/RPC_directory.ml
@@ -43,6 +43,12 @@ let register dir service handler =
       handler p q i
       >>= function Ok o -> RPC_answer.return o | Error e -> RPC_answer.fail e)
 
+let register_chunked dir service handler =
+  gen_register dir service (fun p q i ->
+      handler p q i
+      >>= function
+      | Ok o -> RPC_answer.return_chunked o | Error e -> RPC_answer.fail e)
+
 let opt_register dir service handler =
   gen_register dir service (fun p q i ->
       handler p q i
@@ -62,6 +68,8 @@ open Curry
 
 let register0 root s f = register root s (curry Z f)
 
+let register0_chunked root s f = register_chunked root s (curry Z f)
+
 let register1 root s f = register root s (curry (S Z) f)
 
 let register2 root s f = register root s (curry (S (S Z)) f)
diff --git a/src/lib_rpc/RPC_directory.mli b/src/lib_rpc/RPC_directory.mli
index 8ae3d1e6f187e6cf119eae81f37469639d66a1da..4be09bf5b4898f0e96a8de7568fe9a2a6fd39002 100644
--- a/src/lib_rpc/RPC_directory.mli
+++ b/src/lib_rpc/RPC_directory.mli
@@ -36,6 +36,12 @@ val register :
   ('p -> 'q -> 'i -> 'o tzresult Lwt.t) ->
   'prefix directory
 
+val register_chunked :
+  'prefix directory ->
+  ([< Resto.meth], 'prefix, 'p, 'q, 'i, 'o) RPC_service.t ->
+  ('p -> 'q -> 'i -> 'o tzresult Lwt.t) ->
+  'prefix directory
+
 val opt_register :
   'prefix directory ->
   ([< Resto.meth], 'prefix, 'p, 'q, 'i, 'o) RPC_service.t ->
@@ -62,6 +68,12 @@ val register0 :
   ('q -> 'i -> 'o tzresult Lwt.t) ->
   unit directory
 
+val register0_chunked :
+  unit directory ->
+  ('m, unit, unit, 'q, 'i, 'o) RPC_service.t ->
+  ('q -> 'i -> 'o tzresult Lwt.t) ->
+  unit directory
+
 val register1 :
   'prefix directory ->
   ('m, 'prefix, unit * 'a, 'q, 'i, 'o) RPC_service.t ->
diff --git a/src/lib_rpc_http/media_type.ml b/src/lib_rpc_http/media_type.ml
index 4a00501cd1a42d8df5d1485296f3b9dff2254f36..325d8cddc66184278f21b89f15b002805d618967 100644
--- a/src/lib_rpc_http/media_type.ml
+++ b/src/lib_rpc_http/media_type.ml
@@ -25,6 +25,9 @@
 
 include Resto_cohttp.Media_type.Make (RPC_encoding)
 
+(* emits chunks of size approx chunk_size_hint but occasionally a bit bigger *)
+let chunk_size_hint = 4096
+
 let json =
   {
     name = Cohttp.Accept.MediaType ("application", "json");
@@ -47,7 +50,7 @@ let json =
         @@ Data_encoding.Json.construct enc v);
     construct_seq =
       (fun enc v ->
-        let buffer = Bytes.create 4096 in
+        let buffer = Bytes.create chunk_size_hint in
         Data_encoding.Json.blit_instructions_seq_of_jsonm_lexeme_seq
           ~newline:true
           ~buffer
@@ -68,6 +71,10 @@ let json =
   }
 
 let bson =
+  let construct enc v =
+    Bytes.unsafe_to_string @@ Json_repr_bson.bson_to_bytes
+    @@ Data_encoding.Bson.construct enc v
+  in
   {
     name = Cohttp.Accept.MediaType ("application", "bson");
     q = Some 100;
@@ -89,16 +96,11 @@ let bson =
                 bson
             in
             Data_encoding.Json.pp ppf json);
-    construct =
-      (fun enc v ->
-        Bytes.unsafe_to_string @@ Json_repr_bson.bson_to_bytes
-        @@ Data_encoding.Bson.construct enc v);
+    construct;
     construct_seq =
       (fun enc v ->
-        let bytes =
-          Json_repr_bson.bson_to_bytes @@ Data_encoding.Bson.construct enc v
-        in
-        Seq.return (bytes, 0, Bytes.length bytes));
+        let s = construct enc v in
+        Seq.return (Bytes.unsafe_of_string s, 0, String.length s));
     destruct =
       (fun enc body ->
         match
@@ -120,6 +122,9 @@ let bson =
   }
 
 let octet_stream =
+  let construct enc v =
+    Bytes.to_string @@ Data_encoding.Binary.to_bytes_exn enc v
+  in
   {
     name = Cohttp.Accept.MediaType ("application", "octet-stream");
     q = Some 200;
@@ -138,11 +143,11 @@ let octet_stream =
               ";; binary equivalent of the following json@.%a"
               Data_encoding.Json.pp
               (Data_encoding.Json.construct enc v));
-    construct = (fun enc v -> Data_encoding.Binary.to_string_exn enc v);
+    construct;
     construct_seq =
       (fun enc v ->
-        let bytes = Data_encoding.Binary.to_bytes_exn enc v in
-        Seq.return (bytes, 0, Bytes.length bytes));
+        let s = construct enc v in
+        Seq.return (Bytes.unsafe_of_string s, 0, String.length s));
     destruct =
       (fun enc s ->
         match Data_encoding.Binary.of_bytes enc (Bytes.of_string s) with