SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '868bfb95b338d9eee982d213dcfe9100b02f1849ae829793a6d1c032bec782ac' 
  AND token = 'UY2nqd5tDbeO8HSjkvXSTTvXRoj36esFCfQWtoyaKkM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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