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SELECT 
  1 
FROM 
  tmall_lock_keys 
WHERE 
  key_id = 'f6e54f6cdede44a3c6412060723f010796dca0689141f8dd5fe4b404e2fdb0c0' 
  AND token = '42RosAINkMYvlrTxt8iPaExCvGuJri5z5z0IavSx/Ng=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00797

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}