SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '75b84f0427ebc43cda4395ef74b276748f415ba58725276b77e554b931a28025' 
  AND token = 'EkTO+IDg5LRSXGGdlE3WOG6RQXKEjLHuYLS+sD/QbqY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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