SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '700f40f76b2125b28f7ac776e07df9fc6e7642daae7e937b8e1da005bcbe64be' 
  AND token = 'LpZt15jeo8R7ARPc/kDsiuYGyQEUHnDnhIrStjjkpgs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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