SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6b8740fd55a5176a8dc8e1b37689168f27648d8056a20c3908a194e7c8a23811' 
  AND token = 'UVXJRqg7H9OIwYLhgBm949uRBPQ5eEhP+tFZ44WDpuY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}