Immutable Ordered Key-Value Store API

immutable_store.proto

// The API can be implemented as HTTP API, gRPC API, and/or Go code level API.
// The specification below uses Google Protobuf 3 IDL and gRPC framework:
//   http://www.grpc.io/faq/
// For overview of implementing service with this specification:  
//   https://github.com/grpc/grpc-common

syntax = "proto3";

package immstore;

message KeyValue {
    bytes key = 1;
    bytes value = 2;
}

message KeyRange {
    bytes key_beg = 1;
    bytes key_end = 2;
}

message VersionedDataID {
    uint32 app_id = 1;
    uint32 version_id = 2;
    uint32 data_id = 3;
}

message GetRequest {
    VersionedDataID id = 1;
    bytes key = 2;
}

message PutRequest {
    VersionedDataID id = 1;
    KeyValue kv = 2;
}

message RangeRequest {
    VersionedDataID id = 1;
    KeyRange range = 2;
}

message StatusReply {
    enum Status {
        ERROR = 0;
        OK = 1;
        BADKEY = 2;
    }
    Status status = 1;
}

message KeysReply {
    enum Status {
        ERROR = 0;
        OK = 1;
        BADKEY = 2;
    }
    Status status = 1;
    repeated bytes keys = 2;
}

message ValueReply {
    enum Status {
        ERROR = 0;
        OK = 1;
        BADKEY = 2;
    }
    Status status = 1;
    bytes value = 2;
}

message KeyValueReply {
    enum Status {
        ERROR = 0;
        OK = 1;
        BADKEY = 2;
    }
    Status status = 1;
    KeyValue kv = 2;
}

service ImmutableOrderedKV {
    // Get returns the value bytes corresponding to a key
    rpc Get(GetRequest) returns (ValueReply) {}
    
    // Put stores the given key-value pair.  It is an error if the
    // key already has a stored value.
    rpc Put(PutRequest) returns (StatusReply) {}

    // GetRange returns all key-value pairs stored within a range of keys.
    rpc GetRange(RangeRequest) returns (stream KeyValueReply) {} 
    
    // PutRange stores a stream of key-value pairs.  It is an error if any
    // key already has a stored value.
    rpc PutRange(stream PutRequest) returns (StatusReply) {}
    
    // KeysInRange returns all keys stored within a range of keys.
    rpc KeysInRange(RangeRequest) returns (KeysReply) {}
    
    // DeleteRange deletes all key-value pairs within a range of keys in
    // an asynchronous manner.  Deletions can be carried off in the background
    // although keys should be made invalid upon return.
    rpc DeleteRange(RangeRequest) returns (StatusReply) {}
}

Compared to the mutable ordered k/v store API, the immutable store has no batch transactions because there is no delete only puts, and you can only put once for a key.