SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '521c7d66cef7afebe6ee42c13a179f69045ecb526318264a0f40861bd237f682' 
  AND token = 'bvutMXKT3zZsghFHzc3Ojz9QElrMkGxe5rDGkVZQNjM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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