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SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3351cd4c31aa64b262da08e9b0b35b5c4014e181dc78aa513d8722a8f025d862' 
  AND token = '52zNb5cZgGSVnm+UPBRRwXJMQa8bQrLew3s3PcthwZI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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