SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3c156c2b8fe74c3e2460cf1d6264dee77215d42a98e280f45abbba1a10fa347' 
  AND token = '4LWzslqLBea4RuAL5xpX0lpLdouMEzdKe2t93JIvI8U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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