SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '94b30460593ec2b53e87c887ce1b2d1c29adc2a9aa725d967378ad9c1b538799' 
  AND token = 'UnFQpsWEQSsGf1qAjZ8oPJd04mOTKarT+tJlLqRjQCc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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