SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8cada3e0882304cf48390718fbdb054d5a1abb7972e06966a13f86556be4ba6' 
  AND token = 'PJg9QI/FbmNuvY5N/k4VaCtkw1z9ojOK6w9uOdZJ/6k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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