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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b3b76acc773e783c668d8cb7a149cb4b01502f21f91f2ea20e1fefb3efafe5d2' 
  AND token = 'A/9tnw0ivvpWh7LObkNmOyf/CyR0oXifrC60FxN2lIM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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