SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5939929d1537250e18ef6e86ca273ad1af436f562206926f57cc575bac6beba4' 
  AND token = 'BksOPzbgpff52bU0XHY9Qngedm+ieTFfp99fBPeoPrI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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