SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '27ebe8fc9b01cf066eb732850cef994018bd6fccaef277a6d8a26e1b5a395757' 
  AND token = 'lZrDdLfJu0wVypwZqvzFhdvhPDPS6R3dnVlhp1APmGw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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