SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3a855f50fa2912c011634f913e80b5c9c84b07168103676cc733da2655e8a504' 
  AND token = 'BYV2O4RFIaHsWrieXY9IpVt2FC+B9VKP/1JVElbLvrU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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