SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '03fdb93b06835d38348772968f88a327167b19527e0f0759729fec22f828ec96' 
  AND token = 'gXycum0PTBqfxtlHoswChtYOWaNEDNAL7TMdkymTnMw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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