SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'f840d83ba74f79fcc439a48f3fdfda24a989e9755ec2100ed4e548a0cb7a7fc1' 
  AND token = 'inyV+sHwyRoGO4NXcFfqJWr7RZ8ZkbT5TpVjh2rjf9Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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