SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '78be439ad3d9500315dbdf9273d8201001d1b4e82287a29f2e25b2e74b4783e7' 
  AND token = 'eHq4Nz6w96BNz2cwPVV9RTAJ299nV37xSrpG/NI73LA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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