SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '534a66e4d3649f1fc73bca08aabe554248dee245be5226ab266262e15bf0eda0' 
  AND token = 'E1Ru9mjeAhotecpSpf5jFzrfhe7eY+tTVous2iDclYM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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