SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '205706802e704e947d618fe768c11dd74c77b745b071c3f3d604efba2b122b6a' 
  AND token = 'n/pxwHhrp7JUVZqzgV6JGWL/DWpStG8PA2WAP+GOf5E=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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