SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8c493b6ee8bca435135f34c336a2f522a801d92dd318064970510212da6e56f4' 
  AND token = 'Zo6KmaNCzGdpViTQbhDih7uVFBwBL8fcoluIvP6b8pA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00015

JSON explain

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