SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a8ba041247211b03294710e9189b5e72c7683d44af148519cb27f6d42f546ad8' 
  AND token = '8kBJKHIMwG/wk33GgJvCt52IxI7A4XjI8RZjk6Zbu2M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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