SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '39220b43f3c4c749f8894e370707728c7f2bfcd9fc7a6f165a38a5be7134c1df' 
  AND token = '1tae+6xo9/kpsNqFdzSzHzXtJ5NaTpL8h/aVYZGByNI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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