SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '26839d63b60d5cf69fa42048bdbad7c32013948be8f0d3900aaee6478f8b0b99' 
  AND token = 'wrSFCUH+ha/LiwJgVVDzAPUYr8bIgqli0YtfwHcFi7g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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