SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6022f6bb9f218ff54b592447c0be79e2bd6b2a2cd300e334abbae95269deff8' 
  AND token = '0VQPNwPbWbeoRjRUINolnKFIIwhash2qPp+s5aVLzEw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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