SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '76f51fd4dd1f4ed2640d194ffe42bb405004704688b5bd1bc25c525232b72102' 
  AND token = '8JJ8n0wDZSKyI+BqDdS02vXKyCsnUX9sMqV+lud6XxU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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