SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a9973aa566447fd65c8a130c81593bb5ba4f01f579a61e7dcf4a72d0641cf550' 
  AND token = '6UibDAw7QbItMaML2E3UEKzcCWnomIF8SqztVeyOOv4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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