SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = '6b4790f4b9215fb480cf16a2839225df29a254706552658f42892626b583b087' 
  AND token = '/4GX0F/GXqTiPC1+0gfTDORR8bdTyHIcunr0XTcqYsI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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