SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7b434e014806d94118795bbcd6af504bdaa6946c68819b9df99d83fb00c1697' 
  AND token = 'vXVkbKpJp/3829flK+ixBtZu3YkhWv3y+oTmbYqmYXU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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