SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6321e810fa3d5b26f3f8bce1fe291fa2992960da3642d35acadbb28a61ee72b3' 
  AND token = '2MRQNeYWD9kbj/G1YDWNGo9aScpuGJ5MZMODcq9Qt3s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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