SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f9e4d8b54105ca5902078041337dff98da9688b678508505ea153998d52e4c84' 
  AND token = 'iIUlw81g9wGZRmCec3lvofnd6TRK4zKG8fndt5Icyew=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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