SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'ccb1aa8f757c79967ab6129ec88286baf1f31feedca3f246176a2219541db68a' 
  AND token = 'xKly87KcGXIpv1HSYF2EoGp1pxFsiFekcHHULy0Ytns=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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