SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '645e1e7f525e94d11c1f686dda0a57ee98bd568d565d08649794517e56037341' 
  AND token = 'oHxEW/3UUDp+tMo7FxDRrf6uwKTcxM+jLuOzyEZgltk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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