SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '124f66c1f58cbc9542b0020126657c839ae020d1103a5630caa47f6a378dae3a' 
  AND token = 'THWDCaryNOWd3NaiPpzqP8U3XKZdgegBEmjHcMyf0gU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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