SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79ca1462946e708ad71813f9955d16955fc253665fd6bd976094f54b27a15c54' 
  AND token = 'sucSzLPRdg6GBFmevH4hcBXMyEqDEW+FdzUyZJ3kBI0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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