SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a0409894ba51fee9ec484f9455e5b0d5db467fa137c794597cc84396905d951e' 
  AND token = '2an8GKglRdHKpXy6SvemRylDQqd3T2MGzY6tYAX/kvU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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