SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'b2ae08c7bc76ad863438d158b165b14d476286d7ccd4f99f1769dd4f9dda8e55' 
  AND token = 'CbdrE+zJ8ro1U0rzLqFVYpwNgtNcNdsNG7yocnLmLOw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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