SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '103a497812dce693903913011bb7c7add0dac970044b597f9c880a571f845768' 
  AND token = 'Xb0PnouTQAJVaTcCgAVcvF6GFMW4wi9boVp1gkQfBwo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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