SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '874818ef54a717f4b1bc9dfc4f59f596af7f03f00e0f34a049ddb7b43508c603' 
  AND token = 'DHZmvnpT6kLqwZm+Bel6tWkUjmeon26BFzXJ12KnqV8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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