SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7da3d267f00125c262228ba069cfb890a0b65d5517da1ed836a0913d5aa67e13' 
  AND token = '4aZV0tJsmbYzyT2Ifcy9uZVdJOFhTIZRLBXx/AdJj2A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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