SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'c38ff1a8d61a6343a130201fd1abd9000769bb29f1346828be59439a818c235f' 
  AND token = 'AMxMhUxm74BvPvg5jMZDoc+ZARtmEeZvdV+rCK/LGzg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00036

JSON explain

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