SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '87c86cae45f361d6da0c995fa65bd678aadbe01e3a05559ba1d29a76874e2d98' 
  AND token = 'UN/SjhBna7+3bAEAIneaWpPd0gmXngJdHOIQg5RLIWA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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