Server-Side Flag Evaluation API: Simplifying Feature Flag Access

async Task<ICollection<JsonElement>> MongoDbGetAsync()
{
    var mongodb = serviceProvider.GetRequiredService<IMongoDbClient>();
    var collection = mongodb.Database.GetCollection<BsonDocument>("FeatureFlags");

    var filterBuilder = Builders<BsonDocument>.Filter;
    var filters = new List<FilterDefinition<BsonDocument>>
    {
        // Environment filter
        filterBuilder.Eq("envId", new BsonBinaryData(envId, GuidRepresentation.Standard))
    };

    // Tags filter - supports AND/OR modes
    var tags = userFilter.Tags ?? [];
    if (tags.Length > 0)
    {
        var tagsFilter = userFilter.TagFilterMode switch
        {
            TagFilterMode.And => filterBuilder.All("tags", tags),  // All tags must match
            TagFilterMode.Or => filterBuilder.In("tags", tags),    // Any tag matches
            _ => filterBuilder.Empty
        };
        filters.Add(tagsFilter);
    }

    // Keys filter - exact match on flag keys
    var keys = userFilter.Keys ?? [];
    if (keys.Length > 0)
    {
        filters.Add(filterBuilder.In("key", keys));
    }

    var filter = filterBuilder.And(filters);
    var flags = await collection.Find(filter).ToListAsync();
    
    return flags.Select(x => x.ToJsonElement()).ToArray();
}

async Task<ICollection<JsonElement>> PostgresGetAsync()
{
    var dataSource = serviceProvider.GetRequiredService<NpgsqlDataSource>();
    await using var connection = await dataSource.OpenConnectionAsync();

    var sql = "SELECT * FROM feature_flags WHERE env_id = @envId";
    var parameters = new DynamicParameters();
    parameters.Add("envId", envId);

    // Tags filter using PostgreSQL array operators
    var tags = userFilter.Tags ?? [];
    if (tags.Length > 0)
    {
        var tagFilterSql = userFilter.TagFilterMode switch
        {
            TagFilterMode.And => " AND tags @> @tags",  // Contains all tags
            TagFilterMode.Or => " AND tags && @tags",   // Overlaps with tags
            _ => string.Empty
        };

        if (!string.IsNullOrWhiteSpace(tagFilterSql))
        {
            sql += tagFilterSql;
            parameters.Add("tags", tags);
        }
    }

    // Keys filter using ANY operator
    var keys = userFilter.Keys ?? [];
    if (keys.Length > 0)
    {
        sql += " AND key = ANY(@keys)";
        parameters.Add("keys", keys);
    }

    var rows = await connection.QueryAsync(sql, parameters);
    return rows.Select(x => RowSerializer.SerializeFlag((x as IDictionary<string, object>)!))
        .Select(x => JsonSerializer.Deserialize<JsonElement>(x))
        .ToArray();
}