SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83b9bd9170134d6805e7f23d0138bd36d25a8e50d8e3505dad9a2628e80b77c8' 
  AND token = 'DRqQfvvagtpqTtxh1fEWLbjWdPmXSUexSaHWn3Us61s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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