SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '73f80e245aa5974513c5da2afd8b69b4d1c3b435def4104e1b614c07da95678b' 
  AND token = 'J9w9SvrghYVnGNsKr9+0Ao0WETozk2wlxCz0H/snfB8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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