SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ac8f41ad7654a72b8b766dad67d849a5612b8453a30384aebfd45ae5ee83201' 
  AND token = 'xkTrVjn6JCX3N8kBWDCz8qa3ppzxhjU4EdCwW2k87e0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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