SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6eb8867befcfbde1b3fe838ced156a54a4baf3cfccd7f2feda317c2ba990d13a' 
  AND token = '4nDdPYNa07aFsvl6w2cUY1exg1Sam6ar6AuI2B1q64M=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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