SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '1ac974b949652e2486c1898be758068b422783715913a166204ceadf7e24963f' 
  AND token = 'GffKoUgnn+T/3MAHb1gsAa6HSOTGD+qwfC4m59AjMPM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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