SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '2dc13f2ca186e62a769713dd4444edf68a3e92991b3e0f338f4c59ef2b57da06' 
  AND token = 'RDSW35WgfilYMg8rhuuXfJg/zap+FzhGevQZzdGLjos=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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