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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fdbf7e251443ba12f121cb745ff684dded8c0e3b904fc43742f6b944f467cf99' 
  AND token = '55gllT+9XuqEoiw3af16h61iMgoj1TXmp5Ferbo39Tg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}