size_t block_size() const { return block_size_; }
  size_t max_bytes() const { return max_bytes_; }
  uint64_t max_staleness() const { return max_staleness_; }

  /// The current size (in bytes) of the cache.
  size_t CacheSize() const ABSL_LOCKS_EXCLUDED(mu_);

  // Returns true if the cache is enabled. If false, the BlockFetcher callback
  // is always executed during Read.