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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8d136d7ad9fde5358e4351635becbb4082291a2d743e92e0aed88d0918a81e9' 
  AND token = '1KBJlg5UsldiMHMY3x3C8kqZDPBF4NZs0HhOVVPw4gs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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