SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '15d9fbbf6c27eec6a6857fdb4b339580bd6f68ef762c26e8c0c73a55b863dbc9' 
  AND token = 'Emy15YZJsVZGhUw41gPFyAAJd3WdlPaOuJdUh+l+hTk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00067

JSON explain

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