SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b9a3a88c87bfc8f2b9c221baa6da1159f92dc9cf5b33409977addb30be5ecd15' 
  AND token = 'UvMTYrRCjVuaU87tTum0hLrDwRw/2c0Ox2pcEjyRQug=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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