SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'eee40fc1982f7f10d5ab171b931f078553dae8512dea7e8d6eca7b60a5de5ada' 
  AND token = '168AHwPildNl2eM3nSq9y0b4ig1l+vqSK9S8u902I3c=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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