SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '55fad393ec1a73a911633e9cdce6526c81fc0ac24a5d874bb0850f283c5e4256' 
  AND token = 'tG6lLPoeAfAKh1pfLd9rOXYewFlUBz0UMW1/qAFNnj0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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