SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '4204d749aa542fd48621ec66663e86536743aa68496576dceb1652c10438b3fe' 
  AND token = '79fr3rXoGhFwdvMzJfPz3pHf4ygIwCX775TOGlGYtyg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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