SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8f9a84cc6958f2d52e430471452d211bbbc514783036d45ce1d23d249c123ddd' 
  AND token = 'yiefR6GRKxkF9Q4cTuUg7CNkp+iF1V5SQVaJnzO1FTo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}