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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6a0ddb42d5c8edf9a24e14fe4a81d7bcc79910f0117b8e6c93d74b8faf01be6' 
  AND token = 'zXdTxmxu/EihVErX+Vin4WH18flg/MFDwDgcYf1JOMA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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