SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c35e91e5c1e1d8ee1ea69423565444c8fcc2d0ff9293c75acf638b8e8ad8aa66' 
  AND token = 'PYgFlHJj8sJu3ybgwrNSHrUUNa7oiaMJD31ZMbfkWIU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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