SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a338f6abc59c2b5326fe32b3ed91f3030e4a4580d844d0a316c01e749ec7c7eb' 
  AND token = 'n/v03hPzsKvJFR3pcU4hPagy7AOtltdR7NWGLj+EQZw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}