@achenet

Postgrex.start_link starts a pool of connections that can be named and safely accessed from any process.

iex(1)> Mix.install [:postgrex]
:ok

iex(2)> Postgrex.start_link(pool_size: 5, name: MyPool, database: "example", username: "postgres", password: "postgres", hostname: "localhost", port: 5432)
{:ok, #PID<0.202.0>}

iex(3)> Postgrex.query!(MyPool, "select 1", [], [])
%Postgrex.Result{
  command: :select,
  columns: ["?column?"],
  rows: [[1]],
  num_rows: 1,
  connection_id: 55,
  messages: []
}

If so, is it better to have one shared pid for all handlers, or create a new link to get a new pid with each request?

Depends on your use case. But usually, for small requests that happen often, it’s more efficient to reuse an existing pool of connections.