SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '534307f2f18b08e36514d77146110bed512d06c6699beaf504a1e9ebebd9642d' 
  AND token = 'WRAyKkVtFVv0gLoCiBE+5hfOB9RirZhRImjj86Vptm4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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