SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '7b535c1eb557a8cc907115c75f6639f89891bc4fbadf381d76ee2e39fce7a5fb' 
  AND token = 'uGQKC0QgTfS2mkReuGnkpZAUBYDL58EoFqnId+gtPis=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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