Two related senses. (1) Brand-side: a
私域流量池 is the user reservoir built up via WeChat groups /
企业微信. (2) Algorithm-side, especially Douyin: when you upload a video, the platform shows it to a small initial 'pool' (~500 users); strong engagement promotes it to the next, larger pool, and so on —
阶梯式流量池 ('tiered traffic pool'). Hence creator complaints like
流量池太小 'the pool is too small' = the algorithm isn't pushing my video.