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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '540070b9eb57f23d092c5b4c0a620f7742646c64c71c5296c524e17117a4439a' 
  AND token = 'hbtS1T6vo/zheP1DD17wNpcPnKU0ByeT6k/E3TXgMNI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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