Please describe H/A and scalability purposes more detail (external load balancer, scalability of storage, service discovery). You can attach the picture if it is useful.

Also what will you do in this application to guarantee that the data has been written to the specified storage successfully?

Probably we need to ensure that input serialNumber is not zero.
Something like:
// S/N is zero
if s == 0 {
return c.NoContent(http.StatusNoContent)
}

Json is fine, but are there any other formats which will be faster for sending in client-server applications?

There was a task to create client-server app, why did you decide to avoid from client side implementation?

localhost:/go/src/github.com/painhardcore/emc-testtask # docker build -f ./Dockerfile .
Sending build context to Docker daemon 16.3MB
Step 1/9 : FROM golang:alpine as builder
---> 34d3217973fd
Step 2/9 : RUN mkdir /build
---> Using cache
---> 7f4a8f0eeeeb
Step 3/9 : ADD . /go/src/github.com/painhardcore/emc-testtask/
---> Using cache
---> 51cb858f2728
Step 4/9 : WORKDIR /go/src/github.com/painhardcore/emc-testtask/
---> Using cache
---> a7381a0067ed
Step 5/9 : RUN CGO_ENABLED=0 GOOS=linux go build -o main .
---> Running in 98ed057452f2
handlers.go:7:2: cannot find package "github.com/labstack/echo" in any of:
/usr/local/go/src/github.com/labstack/echo (from $GOROOT)
/go/src/github.com/labstack/echo (from $GOPATH)
main.go:7:2: cannot find package "github.com/labstack/echo/middleware" in any of:
/usr/local/go/src/github.com/labstack/echo/middleware (from $GOROOT)
/go/src/github.com/labstack/echo/middleware (from $GOPATH)
handlers.go:8:2: cannot find package "github.com/tarantool/go-tarantool" in any of:
/usr/local/go/src/github.com/tarantool/go-tarantool (from $GOROOT)
/go/src/github.com/tarantool/go-tarantool (from $GOPATH)
The command '/bin/sh -c CGO_ENABLED=0 GOOS=linux go build -o main .' returned a non-zero code: 1