SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'a3208a826d33c6b80279d7951f1094f6a37210eeaba995507c355a87d3438882' 
  AND token = 'fgMhKaPPv/IspP5G8rN3PmR4r0CzazDXl2pmtvN+oyA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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