C# and .NET

using System.Net.Http.Json;

public sealed record Signal(string Type, string Value);

public sealed class PulseClient(HttpClient http, string organizationId)
{
    public Task<JsonElement> TrackAsync(string sessionId, IEnumerable<Signal> signals) =>
        PostAsync("track", new
        {
            sessionId,
            organizationId,
            signals = signals.Select(s => new { type = s.Type, value = s.Value }),
        });

    public Task<JsonElement> RankedCatalogAsync(string sessionId, int limit = 24) =>
        PostAsync("catalog/ranked", new { sessionId, organizationId, limit });

    public Task<JsonElement> SessionAsync(string sessionId) =>
        PostAsync("session", new { sessionId });

    private async Task<JsonElement> PostAsync(string path, object body)
    {
        var response = await http.PostAsJsonAsync(path, body);
        response.EnsureSuccessStatusCode();
        return await response.Content.ReadFromJsonAsync<JsonElement>();
    }
}

builder.Services.AddHttpClient<PulseClient>(client =>
{
    // The trailing slash matters. Without it, a relative path replaces the last segment
    // and every request goes to https://api.thepulseapi.com/api/track instead.
    client.BaseAddress = new Uri("https://api.thepulseapi.com/api/v1/");
    client.DefaultRequestHeaders.Add("x-api-key", builder.Configuration["Pulse:ApiKey"]);
    client.Timeout = TimeSpan.FromSeconds(5);
});

public class CatalogController(PulseClient pulse) : Controller
{
    public async Task<IActionResult> Category(string slug)
    {
        var sessionId = Request.Cookies["pulse_session"];
        if (sessionId is null) return View(DefaultOrder(slug));

        try
        {
            var ranked = await pulse.RankedCatalogAsync(sessionId);
            return View(ranked);
        }
        catch (HttpRequestException)
        {
            // Ranking is an enhancement, never a reason to fail the page.
            return View(DefaultOrder(slug));
        }
    }
}