SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b76e3c81d6f8b245e310714502696a7ccc2ac1aab55b8341d38c63a070f66f26' 
  AND token = 'I+W/wsB5VHV+Hc9b3RMhgfz9nPmdTUPmKeN7OlrvGO0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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