SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2a52756290336875006141731d78449073b2f039c29682a271024c1bac1a24cd' 
  AND token = 'TX2mmkiW6Py3TlpnYml1FRQtdJjuCzWPFp9Jy7mkXfs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00054

JSON explain

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