SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e4bb7c684168ec3bc00497676e07a6d2698c8440ce8ce756cc1fe43e31213f42' 
  AND token = '1WnkWKgXysf7ntYQHVsRSGFhjBzUPV6vfpZ2swvuP00=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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